Some just do not see the bad in their kids...ever. Or they make excuses for such behavior, once excuse is made they act like it doesn't exist. Further if kid does "x" well they act like the bad stuff "shouldn't count".

These have been a few of my experiences anyway. 

It's all utter bullcrap and likely will not change. You will have to decide if you can deal with it or not.

FWIW, there are kids who are well mannered, considerate and quite likeable outside the home while being little terrors at home to their families.  I'm not saying that's the case here, but I've seen many instances of this.  And then there are the parents who just have blinders on where their kids are concerned.  Or maybe your GF knows you see the worst side of her kids so she's trying to let you know that they do have it in them to behave by bragging about what others have said about them.

DH use to try to brag about skids. He really use to think skids farted rainbows. Skids would be rude to him, talk down to him like he was hired help and he couldn't even see it. I pointed it out and told him I couldn't be with a man that allowed a CHILD to talk to him like that. I told him I was embarassed for him and I couldn't watch him become emasculated like that by a 5 year old girl. That was the start of DH opening his eyes. 

    Skids are very mediocre. DH would try to brag about their reading and math level. One was 2 grades ahead on reading and one grade ahead on math. For DH, he was horrible at english and his family never really acheieved much in school so that's why he says he was so proud. I just ignored his bragging, that level of "achieivement" is way behind in my family. I ignored until I couldn't take it anymore and finally I asked him why he was proud of that and had to broadcast it every chance he got? I showed DH my son's levels in reading and even math (his worst subject). He is younger than skid#1 and was waaayyyy ahead of her in reading and even math. I asked him to explain if that level of achievement was really something to be that proud of in his family? I told DH, I don't understand because in my family, skids would be in tutoring. He shut the hell up about skids "achievements" after that. No DH, your kids are very mediocre, you just didn't know about my children scoring way above their grade levels because it is just expected in my family. When his 11 year old daughter couldn't turn bath water on by herself, that moment was also gold and the complete nail in the coffin for DH and his stupid bragging. 

Hey new to step parenting guy - this is a common and sometimes really annoying thing. I'm probably the other way and don't brag about my son enough. My partner probably brags on my son more than I do and on his own kids, too. But here's the truth - I am really, really proud of my son, while being aware of his deficits. Some people aren't able to see their kids as rounded people, with strengths and deficits and some people just don't like to admit their kids' deficits. Maybe that's your GF, maybe it's a little more complicated than that. 

It is harder to be proud of my stepkids because I didn't 'make' them and I haven't been in their lives that long. But they are cool people. My older SS12 is easier to brag on because he's just more open - but he has many annoying properties, too. His BM finds him really annoying (I find him less annoying because I spend less time with him and the things she finds particularly annoying -e.g. his smart mouth - I actually find funny). SS9 is a mystery - there's a kid who really hides his light. He calls himself stupid (he's absolutely not) but he's not the glaringly academically kind of bright that SS12 is or my BS10 is. (Hey, I just bragged on them both!) I see in SS9 the kind of struggles that my brother had following me in school in a small town - I was academically gifted and he just found the expectations too much I guess even though my brother is just as clever as I am. 

What you have to remember is that change of family formation - a new step parent or step siblings - is hugely stressful on kids. They have all these conflicting emotions plus all the daily stuff of just trying to learn how to share space with a new person with their new habits. So you may not be seeing GF's kids at their best. It is also very common for kids to behave well outside the family and be awful at home. And it gets worse as they get older. I just visited some friends and their sweet adorable 11yo has turned into this hulking, silent sulking 12yo. They KNOW it. But they made a point to say how well he's doing in school and at church - I don't mind because I'm happy their son is achieving well outside the home and just sorry for them he's a gruff little monster at home. I also know that this may be my not-too-distant future with any or all of our three. 

The other thing to remember is that all children are both amazing and awful. All kids CAN be disrespectful, lazy and rude. It is our job to turn them into polite, considerate, hard-working adults over time.  She may be highlighting the amazing in her kids because she knows you're seeing mostly the awful. My son has really improved since my partner came into my life because his dad was terrible to me. Verbally abusive, very critical, very disrespectful - just awful. And that was the way he saw me being treated for his whole life so of course he modelled that. My new partner is respectful and loving. We have a calm and happy household (usually). My new partner has higher standards for kid behaviour - and I have to admit that in my darkest days in trying to recover from an abusive marriage, I let those slip. We are gently introducing new standards of behaviour in the household so that all the kids are held to the same standard while still respecting their differences. 

Mate, I just replied to your other forum post. It sounds like your gf is a bit pathological. Sorry. 

In my experience, those who constantly brag about their awful kids are trying to change people's minds about their spawn. 

My best friend's sister has three hellions, who are the most amazing creatures if you talk to their mother for 45 seconds. If you observe them for the same amount of time, you realize they are a pack of spaztards who don't listen and leave a path of destruction in their wake. But mom tells everyone who will listen about how above average and superior they are in every way. 

These braggart parents are trying to convince us that our reality is wrong; that what we SEE and HEAR is wrong; that their opinion of their kids is RIGHT, no matter what we observe.

I don't know why people do this, honestly, ie brag about their kids.  It's guaranteed to make the person they are bragging to hate the kid's guts, even if they didn't before, lol.  

My DH seems to think that praising my SDs' every tiny action in the world is going to make me more positively disposed towards them - but it actually does the opposite. 

We are in a kid-centric period in the U.S. Our neighbors laughed when their son had to take a drug test for a job -- they joked that they had cranberry juice coming out of the spigots instead of water so he'd pass. I was surprised they would tell us that when they hardly knew us.

Your GF may be wishful thinking or avoiding the truth, or maybe she just wants others to think she's a really good mom. So many parents now think their kid is nothing more than a reflection of them. Totally narcissistic, IMO.

She's doing her kids no favors. Many kids get through bad behavior without consequences and I think they grow out of it. Maybe hers will get lucky. Maybe not. If they aren't lucky, she won't be able to avoid the truth or the bad reflection on her.

My parents were the opposite, but they are old school. They still think we're awful people!

BM brags about her kids ALL THE TIME. Now in her defence the skids are good kids, they are polite and friendly, they are not rude, they have jobs and are generally doing well in life. 

So, BM can definitely brag about them to some extent but she never stops. I’ve heard from mutual acquaintances how irritating she is. If your child has done something hers did it too, only better. If your child plays a sport, hers both got scholarships for their playing abilities. Your child’s working, well hers both have great paying careers! 

People have walked away from her mid conversation because they are tired of hearing how wonderful her kids are. 

I think in her mind it makes her a better parent because her kids are doing well. She brags about them but it’s really all about her. 

Is your gf a narcissist? Narcissists see their children as extensions of themselves, so of course they're wonderful!

Some bios are narcissist and feed off of the compliments and recognition their children get because their kids are an extention and reflection of them and how great they are. Like most humans, some do it for validation purposes. Some insecure parents will take any action, good or bad, to highlight or validate their logic. Case and point: the other night at my skid's tball game, he got out and stomped his foot in anger as he marched off the field. Narcissist BM proudly declared to the crowd, us among them, "there I am" laughing. To me and DH it was embarassing because it was a display of poor sportmanship. He was clearly out and that is how the game is played, there is no crying in baseball. But to BM, this was validation that SS has some of her characteristics she can claim for herself instead of letting him be his own little human with his own feelings and choices. 

When I read 'amazing' I do not believe a word of it. Too many times I have read here about amazing husbands or SOs and really, they aren't. When I read 'beautiful' I think that person is being very shallow. Looks are not everything in fact they are unimportant. Very attractive people can have appalling personalities.

My kids are nto in jail, legally working , paying their bills and law abiding and good citizens.  And really that is all you need to know about anyone.