It really depends upon some things you should consider first- did your sister have the power to stick by you, or was she prevented from doing that by your parents? Was she still at home and dependent upon them for everything when they threw you out? She may not have been able to stick by you closely at the time- so give that some weight.
She may or may not feel comfortable being the ringleader should you appoint her MOH.
It would probably destroy your relationship if you didn't ask her to be a BM, but only you know how close you could be. If she disapproves of you now and sides with your parents, then it's easy to see why you wouldn't ask her. But if you are now rekindling your relationship, it's crucial that you ask her, even if this is tentative and new. And you may even want to NOT choose an honor attendant at all, but just choose those three people who are nearest to you, including your sister, and leave it at that.
There is danger in ranking the people you love. In this case, you should be very very careful, and rather than feeling pressured, look at this as an investment in your future relationships. It's your one chance to tell her she's still important- and you know how that feels.