but I could absolutely imagine stories in which her decision to become involved with a man, or gradually closeness to a male character, could make sense even in the context of her history and canon interactions.

as a total closet (mostly) S/T fan, I completely agree with you (and as a newby to reading Tara in anything other than a ff relationship other than S/T)... and it's part of the reason I've had a tough time finding fics that work, even in S/T ... it requires someone deal with the characters making a pretty huge jump that requires time and fairly close attention.