I totally agree with you, some kids, like some adults, you just don't like and are unlikely to ever do. The question is whether this alone should be enough not to take a relationship further.
My OH used to go out with a woman with two children. He got along great with the eldest but couldn't stand the youngest. From his perspective, she was a spoiled madam and felt he couldn't relate to her in any way. They dated for a while, but she wanted to take things further and move in together after 18 months. From his perspective, there was no way he was going to do so because of the child. It wasn't the only reason, but it certainly contributed to it.
When we met, he made it clear that he wanted to meet my children earlier on as it was important for him to be sure that he liked them before taking things further. I totally agreed with him because from my perspective, I wouldn't have wanted to take the relationship further if he didn't like them. As it was, they liked each other from the start so things progressed.
Still, it is never perfect. DS entered teenage-hood and with that, becoming much less likable. My OH struggles with it and doesn't like him much at all at the moment. He feels guilty about it too. The way the matter is being dealt with is that they both tend to ignore each other and it seems to work somehow. I am however quite confident that once that stage is over, they will rekindle their relationship.
If you don't like your SD, you have two choices. Either try very very hard to focus on the positives, ie. the reason why your OH thinks she is wonderful, and try to establish some sort of relationship that ignores the things you really don't like. If that is beyond what you can do, then take a step back and let your OH parent her. For that, you have to be prepared to let him do what he wants. What you can't do is take a step back, but then put pressure on your OH to change the way he parents her as that is very likely to lead to the road of resentment.
The difficult question is whether you could be honest with your OH without feeling so hurt that it will impact on your relationship.