Without getting into extreme detail: My sister is 13 years older than I am, and we are not close. She is, let's just say, the black sheep of the family. Should I feel obligated to invite her to my wedding just because she is my sister?
Family matters are the toughest ones. But the bottom line is this: If inviting her is going to cause you a lot of grief on your wedding day, then don’t. On the other hand, if her presence isn't going to aversely affect you, and her not getting invited might create even more of a problem, then extend an invitation. Remember, just because you invite her doesn't mean she'll come.
Though you shouldn't feel obligated, you should definitely give it some serious thought. Talk to your parents and other siblings (if any) about it and see what they think. Chances are, if you're wondering whether to invite her, you probably should. But only you can really answer that question!
See More: Most Asked Wedding Questions , Family & Parents