There are a lot of “if’s” in your post.
True, that.
If (and again, that's a big IF) Bachmann suffers from migranes severe enough to literally incapacitate her, even infrequently, then she has no business running for President.
While I'm admittedly not a fan of her running for President, I don't think she would be so irresponsible to do so with such a known medical condition. Therefore, the most logical explanation is that the allegations are at least exaggerated.