Love is not a "should" emotion. You can't force it. You don't love her. So what? You're kind to her and that's enough. Being the adult in the situation doesn't obligate you to love a kid that's not yours.

It sounds like you've made a decision to disengage, which is probably best. She has two parents that need to step up and teach this child about showering and good health.

I would suggest having a conversation with her about appropriate compliments. That if her mother ever heard her say that SD wishes you were her real mom, it would hurt her mother's feelings, etc. It's not innocent, it's a manipulation attempt. When she says I love you a 100 times, respond with a "that's nice". And then ignore her. It's ok! She'll live, it won't scar her. Tell her to go play or go find her father or go outside but you don't have time right now.

Remember, she will repeat behaviors she gets 'rewarded' for, even if the reward is negative attention. "Fake" it when she's being a good kid and listening or being actually nice. When she's bad, make her father deal with it and Walk Away.

You can't make yourself love someone, no matter how much you try, so let yourself off the hook. It has nothing to do with you being the adult or whatever. You don't love her. That's understandable, that's ok. Don't be so hard on yourself.

I think you have described a common theme with skids, espe vitally sds. I know they all get to that point, especially the more the parents don't work together to keep the child from manipulating both sides. You could easily be describing both my skids, more closely sd13. I did love her at one point, she used to be a good kid. Now she believes she is a victim in EVERY situation (the divorce was about herm kids at school are mean, she as a "boyfriend" at school who was really touchy, so he was abusive, though she admittedly never told him to stop touching her, etc). Hygiene has been an ongoing problem forever with this kid. I would be happy if she brushed her teeth everyday (instead of wasting all the money we are spending on the braces), you are not alone. There are moments I still the I love sd, then she acts an ass again and becomes very mean. After she threatened to hit me, then threatend to put a fork in my eye at the dinner table, then told her dad I didn't deserve to sleep in the bed with him, I should sleep in the care with the dog, slowly my feelings have changed. Everyone around here, counselors include talk bout her abandonment issues (which are imagined, but according to the counselor an issue because she truly believes it, victim much?) there is an expectation I should fill a void for her since she refuses to talk to her mother. Dh understands, I am not here to be a void filler to a kid that s so hateful. It does not make one receptive to caring for a child, when the child treats that person like crap 99.9% of the time.

Cut yourself some slack. Start putting more and more of the responsibility for the Kid on dad. It won't be easy, it's a lot like acing a horrible roommate you can't make move out. Cone here often and vent so the kid doesn't get it.