If the parents and remaining guests blame her for "making" the other guests decide not to come or somesuch, that's their own problem, too. If anyone did that to me, I wouldn't bother with trying to have them in my life, either.
Sorry, but I just don't see the point in placating people like this. Personally, if any of my family members decides that they don't want me at family gatherings post-transition, I'll be saddened, but I'll live with it and I'll be fine never talking to any of them again in my life. I'm not going to make concessions or beg for their acceptance.