Gender politics dating
Not to mention all the possibilities of using Gender Bender stories as metaphors for transsexuality...).Also contrast with Easy Sex Change, which deals with idealized but realistic takes on the Transsexual experience. If the character belongs to a species that does this as regular thing, see Sex Shifter.Male-to-female transformations tend to vastly outnumber the opposite when this trope is in play. It might be Played for Laughs, Played for Drama, or even played for horror if Loss of Identity or an unusual amount of Squick is involved.
Depending on the medium, genre, and storyline, this may be a one-time temporary change, a recurring change (causing the character to jump the gender line often), or even permanent.
She's a Man in Japan is basically "Gender Flip via Localization," where Executive Meddling results in a character's sex being changed to meet the perceived needs of another market.
But as with the aforementioned tropes, Gender Bender characters who previously wore a distinctive outfit may wear a Gendered Outfit, tailored to their new sex, after the change.
Sometimes this is played straight, but (particularly when the crossdressing is Played for Laughs) it's often a case of Informed Attractiveness.
In such scenarios, despite the "new woman" looking mannish and homely to the audience and most characters, someone will unaccountably be smitten with "her." Hilarity Ensues as the crossdressed hero tries to fend off the advances of an unwanted suitor.
If Shelley reconfigures from each termination in a form suited to "protect" him from that method of death, then a female version would make sense.