I may be off track since we have little detail, but to decide to disassociate probably means that she has been hurt in some way. I think apologizing for these injuries might help. Maybe she has been judged, when God should be the judge. With sins such as homosexuality or abortion, we should never make any statements like she is going to hell for her sins because we don’t know where her journey is going to take her. As a Catholic, you are to show love to her and not condemn her.
If you are able to follow EVERYTHING the Church teaches us, then I think you’ll be able to work this out with her through love. However, if you are anything like me, you will find your temper and your frustration getting the best of you and perhaps saying things too harshly.
She needs to show some respect for your beliefs by not trying to force her attitudes/opinions/lifestyle on you and your family, but you might be able to give her a little room to just be your sister and not “the one going to hell for her sins”. Is she Catholic (fallen away)? Hopefully, if she is Catholic, you will be able to remind her that we all find it difficult to live according to God’s will and we all commit some sexual sins or another that could send us straight to hell (contraception, masturbation, lust, adultery - tons of temptations), but that God forgives us through Confession and repentance. It is trying to improve and trying to understand God’s will that is really important, isn’t it? Many of us have the same sin that we repeatedly commit, but it is a very personal thing. It is between your sister and God (and pastoral guidance) and Jesus will know what is in her heart and judge her when the time comes. Maybe her family has tried to do the judging and has used the teachings of the Catholic Church as a weapon against her. Maybe not.
maybe you need the space right now, but if you’ve been harsh with her, I’d work on forgiving her and apologize if you said hurtful things. She needs to know that you love her and that you know that you are also a sinner and that you know God will do the judging, not you. Does this fit the situation?
If she is misguided about Church Teaching, then get her a book to inform her. Maybe something short like Why do CAtholic Genuflect. If she doesn’t understand what the Catholic Church really teaches, then maybe some info. will clear it up. Knowing that we believe that human life is a gift from God might help clear up things such as abortion. At least she can surely see why we’d be against killing something that we believe God gave to us as a gift. She may not believe as we do, but hopefully she can understand our “philosophy” on the topic of abortion.