While this is typical "normal" behavior for her age, I would suggest looking at her diet and removing sugar, food additives, and possibly grains and/or dairy. What she is doing is not "normal" to me, but it sounds like something more going on than mom not disciplining. To keep from telling her no all day, give her choices when appropriate. "Do you want to put your shoes on yourself, or do you want me to help you?" instead of, "Put your shoes on," to which she can just refuse. Make her feel like she is in control, so when you HAVE to be in control and tell her no, she hasn't heard it 20+ times already. The older she gets, the more choices she will have, but always give two options when possible.
"Do you want pig tails, or a barette in your hair?"
"Do you want to wash your hands, or brush your teeth first?"
"Do you want eggs or yogurt for breakfast?"
"Should we go for a walk, or go to the park?"
As long as you don't care which she chooses, you all win. And this is attention that she will eat up.
Good luck!

It's almost impossible to fix and set limits for any kid if one parent is setting limits while the other one isn't. With your SD spending every other week with BM, you will end up trying to reverse damage that BM has done all week. I know exactly how hard that is and our BM only visits once a year! BM did significant behavioral damage to SD and we spent months trying to retrain her back to normalcy. I wouldn't blame you for wanting to leave. It's a lifetime of hardship with a skid who gets half their influence from a bio who does the opposite of what you do. Resenting SD is perfectly normal.

I have a 2 year old GS and he doesn't behave like that. Oh yes, he has an occasional meltdown but then it's time out and he doesn't scream for 40 minutes of time out, it might be about 30 seconds and then that's it. He understands that time out doesn't end until he can calm down. Frustr8d1 has it right. One parent can't fix it when it's one on/one off. You didn't talk much about how your fiance handles this situation but unless he is really stepping up big time, it looks like you will always have huge problems. Your little baby should be your first concern. She will only be little once. I know it's hard but, I'd run fast and far!

What Frustr8d1 said is so true. My SD only sees BM on the weekends but it takes about 3 days for her to start acting right again after she gets home.
She has no rules, no structure, and no discipline there. She is pretty much free to do what she wants, when she wants. Mind you, she's only 6 years old. She has no bedtime there, nothing.

It is impossible to raise a child correctly when you have the other parent sabotaging your efforts. I've been with DH since SD was 1 and while I do see some improvement (no thanks to anyone but myself), SD is still very bratty and entitled.

To answer your question, YES it is perfectly normal to resent your SD, especially in this type of situation. I feel the same way you do. I dread her coming and can't wait for her to be gone. I just hate it.

I feel the way you do. My BF's daughter, who is 3, is with us on the weekends. She has the worst attitude. She cries constently and is mean to everyone, her Gma, her dad, myself, everyone. I understand that she is young and this behaviour is looked as "normal". We have rules in our household, and at her mother's, she gets away with everything. One time when her mom picked her up, she didn't want to go, so she slapped her and pulled her hair. Of course BM didn't do anything just let it happen. I agree with what pp said, it's not going to change if only one parent is disciplining. Every weekend she gets worse.