That's friggin' great. Well, the doctoring part. In someone with MG symptoms who has a high striational AB, the chance of a thymoma is super high.
It sucks that she probably has a thymoma. It is possible that once they remove it, her symptoms "might" lessen or be gone. Might, maybe, possibly . . . I sound the way doctors talk.
You know a good surgeon, if I remember correctly.
I hope she will now pay close attention to what her body is saying to her. She should get a lot of rest before any surgery. She should also consult with pulmonology beforehand, because the anesthesiologist would want to know what her stats are.
I also hope they're careful with any pain meds, like morphine! You know the drill.
It really is a relief to know what's going on. I'll bet she's so grateful to have a sister who has MG. That always sounds awful, but you know what I mean.

Annie