Recently, a hetero cisgender asked me the above question. I remembered questioning my relationship with J. As a hetero cisgender partner to a man who transitioned M2F, his transition caused me to question my own sexual preference. I struggled with societal views and judgments, and wondered how I would be perceived in the relationship if I stayed. I wondered what our sexual relationship would be like on the other side of J's transition. My comment to her question follows based on my own experience.
If you are a heterosexual female, and "he" becomes "she" your sex life will change. You may find yourself in a lesbian sexual relationship. Do you wonder, like I did, that if you stay, and you find pleasure and satisfaction in your relationship with your partner if that means you are a lesbian? or, bisexual? I thought, maybe, I am simply, "bicapable".
"Bicapable" is a term I coined to describe the relationship between an SO and "A PARTICULAR person (husband/partner) who transitions M2F. THIS partner whom you have established a sexual relationship with as a "he", and with whom you have a "HISTORY". I believe it is possible to have a gratifying sexual intimate relationship to each others mutual satisfaction, after "he" becomes "she" because you know and understand each others needs. At the same time, you know in yourself, that in any other circumstance, presented with a lesbian sexual encounter or relationship, that you would have no sexual interest. This is what I mean by "bicapable".
So many variables make up one's own ability to enjoy being with another person in an intimate way.
It is no one's business but that of the two of you with regard to how you express your sexual nature when together. In any relationship, it is the couple that defines what that is. Self-exploration, curiosity, and experimentation can go a long way to contributing to personal growth. And, I believe a relationship can grow and flourish if done with mutual respect, self-awareness, consent, and care for another person.
My suggestion was to talk to her partner about her needs, likes, dislikes, fears, and to be honest, and sensitive to her partners needs as well. I said, "You might be surprised at what you discover about yourself, and your partner. Could you discover you are a lesbian? Maybe. But you may come to realize that by nature, you are not a lesbian, but with THIS person, in THIS relationship, you are bicapable. Thoughts?