Take, for example, the heterosexual woman who later develops an attraction to women, and begins to identify as bisexual or lesbian. She may have experienced this attraction throughout her life and not picked up on it—perhaps she didn’t meet the right woman, or she was living in a repressive environment where homosexuality was not accepted. Or maybe her sexual orientation actively shifted. The attitudes of those around her will be dismissive and unpleasant, as people attempt to erase both her past as a heterosexual and her present as a gay or bi woman.
Though her sexuality has shifted, she remains fundamentally the same woman. Her past history doesn’t magically vanish, and she may even look back on it with fondness or gratitude for the relationships she had. Likewise, people may move through other sexual orientations depending on circumstances, their current stage of life, and other factors; the asexual who later realizes he’s gay, the lesbian woman who develops a bisexual attraction.