It sounds like the good thing is that at least your skids are all over 18. Since your husband won't back you, and gets defensive, the only option left is to disengage. It's temporary at least since she lives on campus. Be distant but polite to her. Hello, goodbye, i like your shoes if you are feeling generous. If asked directly how you feel about something be honest but otherwise be noncommittal. If she leaves a mess, ask your husband to please clean it up. Minimize her effect on you and know it's temporary. And never, ever allow her to move back in full time. 

Rant on, that's what we are here for.  I can tell that you've put up with years of Stephell, like most of us.  Here's an outsiders view:

You bought supplies and a nice mattress cover because you had a houseguest coming, and she is a relative so, of course, you layed in supplies and equipped the bed comfortably. Our relatives (sister, cousin) seldom thank us for this.

BM's poor animal history is beyond our control as long as she doesn't dump any more pets on you.  You are a good person who handled OSS's cat problem humanely.

SD has no clue that mentioning cleaning at her mom's brings out her lack of help at your house.  Frankly, as an 18yo college student, it's probably too late to retrain her.  If DH wants to clean up after her, wonderful, don't you do it.  "Honey, SD forgot to empty her trash can, would you please get it?"

I long ago decided to overlook my SKs odd food choices and my life improved substantially.  I thought their food choices were personally insulting to me, too ( big fast food preference). I now think it was a preference for the taste consistency of fast food.  They hadn't been exposed to very many foods.

The biggest issue, from here, is the upset with DH.  For me, that was always the worst.  If I were you, I would disengage from SD.  Don't discuss her with him, don't argue with him.  No special cooking for her, no baking. Just be civil and polite to her.    She can furnish her own supplies, feed herself, etc.  He can clean up after her.  She is 18, she is on her way out.  Live your own life.

You sound like a good person with a lot of love to give.  She sounds like a normal, self-absorbed 18 yo SD.   Turn your love toward your DH and others in your circle.  Good luck.

Ah I agree with most of what you have to say but I think you are way to sensitive about her eating ramen at this point I think anything even the most insignificant would piss you off 

Sounds as if you're feeling frustrated and resentful, which is understandable. Adults between the ages of 18-22 are often a huge pain in the butt, and it's very common for there to be strife between the old bear and the young bear. It's basically about territory and resources. You're a good candidate for disengagement.

First step to gaining emotional distance is, stop throwing pearls before other people's swine. Your H's daughter is HIS guest and HIS responsibility. No tampons? She's an adult and will figure it out. Bed is too hard? Oh? Many people prefer a firm mattress. Garbage in the bathroom? Tell your H. The goal is to have the problem handled, not control how it's done. Your DH gets to clean up after Miss Piggy. She doesn't appreciate your cooking? Good, more for you. Don't cook for her. Quit treating her as an honored guest, and refer all matters concerning her to her father.

You are NOT obligated to care about this girl, or do anything for her. In doing so, you only set up a scenario in which she fails and you get aggravated. So step back from all things skid, and recategorize her in your mind as simply an extended relative of your H's. The more emotional distance you can create, the less attachment you have to your H's baggage, and the happier you'll be.

Disengage completely. I didn't cook extra for skids over thanksgiving. We are enjoying our leftovers and we plan to eat them all before skids get here tomorrow morning. Don't do anything special for her. I stopped doing anything special for my skids over three years ago. They don't appreciate it. Funny story this month  SD tried to give me a hint that she wanted me to pick up a plant for her dads birthday as a gift from her "maybe if I could get a plant for him that'd be great. If you're going to the store soon let me know or I don't have to go either."  Pretty ambiguous so I just let it go. I said not sure if I'm planning on going to the store but will let you know if I do. Well come time to give gifts she had none to give her dad lol!

Time to really disengage. Your SD has shown you who she is. You know how this will play out - you will always be the bad guy, no matter what, so just back out gracefully. Ex Julie had some ex-cellent suggestions.

SD14 Munchkin, as sweet and kind to me as she is, and has been, drives me crazy when I hear about how she cleans and organizes at her mothers house, when she doesnt even flick an eyelash in attempt at doing any cleaning here (Unless its her own room, and even THAT takes teeth pulling and several acts of God.

I wouldnt take the ramen and cleaning and cat thing personally. She sounds very thoughtless.

I would instead focus on your DH. He gets defensive if you mention SD? OK, nevr speak of her except in generall terms. She makes a mess, he can take care of it as long as it is taken care of.

Not your circus and not your monkees. Let him clean up the monkey sh!t.

Buy a case of Raman Noodles.  And that it.  No nothing for her 

I agree. Go ahead and vent. I dont get the whole tampon thing. My SD does the same thing. I dont like going into the bathroom and seeing something in plain sight that has been in her v-jay jay.  

Anyway I understand your point about the Ramen. It pisses me off when I'm making a meal and a skid or my own kid comes in and starts making something else. My own kid I will tell them to get out of the kitchen and wait for dinner. With skids I've learned to let it go but I stopped buying foods that are easy to make cuz then they eat all the snack foods and leave nothing for anyone else.

As for buying things for SD give it up. Dont do nice things for people who are not nice to you. And dont make people a priority who only see you as an option.

I'm buying my SD a greeting card for Christmas this year and thats it. I told DH that any presents he wants for her he will have to shop for them himself.

Oh my god, girl!

That was my SD's level of aggravation too -- just those nearly unnoticeable things that, of course, her TARGET would notice! Your SD is a clever one! She has them wrapped -- better be extra careful of that one!

I thought the bloody tampons in the can and the ramen noodles were so MY stepdaughter! My SD used to leave her thong underwear laying on the bathmat everywhere she stayed, like she just had to. And the other thing that came to mind was that we had to pay for my SD's gown when she was a bridesmaid in our wedding, which I didn't mind because she was in college, but no kidding -- the DAY AFTER my wedding, at the big fancy brunch for everyone, she said in front of so many of us, that she was going to sell that gown on Ebay. It had come up because my nieces said how much they loved their bridesmaids gowns and that they were going to wear them to college formals. Yea, that's when SD dropped her nasty bomb.

Beware, this dynamic over years can corrode a marriage. I felt like I was handling it all those years I was laughing about it, but the real bill had not even been invoiced yet. Now I see there's a lot of damage from it all.