It's never bisexual, always lesbian, despite the fact that she's clearly straight.

I wonder about this. Some possibilities:

1. Bisexual wife is not "validating" enough for transwoman - we see examples of this mentality among AAP transmen on the daily, it seems, and I would imagine that AGP transwomen are probably more successful at convincing their female partners to change their identity than AAP transmen are their male partners (do they have any...? Seems like AGP transwomen might be more likely to have and keep partners in the first place if it's harder for women to leave abusive relationships).

2. Bisexual erasure among older generations - Older gens (millenial, X, etc.) are more likely to be married at this point in time than are gen Z, and I think there is more anti-bisexual sentiment among older generations, so perhaps a straight woman pressured into stating she's not straight, doesn't think that being bisexual is an option. Might sound silly but the few times I've had bisexuality come up in conversation with (straight) people much older than me, they thought it doesn't even exist and is just "confused people" or something.