When I worked at a gender identity clinic (1980-95), the clinic’s policy was that heterosexually married male-to-female transsexuals had to get divorced before we considered them eligible for sex reassignment surgery.
This policy was in place before I joined the clinic. That reason for it, stated by the clinic’s founding psychiatrist-in-charge, Betty W. Steiner, was that this prevented the clinic from being sued by the patient’s wife for alienation of affection.
Be that as it may, the policy may have had the effect of discouraging the patient from nourishing the fantasy that his wife would remain in the marriage and accept it as a “lesbian” relationship. It was not rare that biologically male patients, who were still living in the male role when they initially presented at the clinic, would express the hope that their wives would accept them as lesbian partners and agree to stay married.
It never happened, as far as I know, that a woman married to one of our patients reimagined herself as a lesbian after her husband transitioned. I do remember at least one case where a woman continued living with her transitioned partner after their divorce for financial reasons.
PS: I wrote about male patients because there were no female-to-male transsexuals who were married to men when they presented.
PPS: There has been at least one well-known woman who stayed with her husband after he transitioned to the female role and, in fact, became a trans activist ally: en.wikipedia.org/wiki/Helen_Boyd