Maybe I'm dense, but I don't see a logical fallacy. A "flaw" would depend on how you define it. Please elaborate.
I'm not Allejandro, but I interpret his comment like this:
"Should Ann have to sit out so that Bob's beliefs can be accommodated?" is a legitimate question, but so is "Should Bob have to train with Ann so that Ann's beliefs can be accommodated?" The only answer to this is deciding whose beliefs are worth more and accommodate those beliefs. Unfortunately, logic does not give us the tools to make that decision. Acting as if it does, would be a logical fallacy. One that in my opinion Mary did not commit, as she did not claim to use 'pure' logic to reach her conclusion.
Fact is that there is no objective means to decide whose beliefs are worth more. So by accommodating Ann but not Bob you're making a subjective decision about the worth of the beliefs of the people involved. That's perfectly ok (How to survive otherwise?), but I do think one should be clear about it. (Not much of an issue in this thread, I think.)