Demigirl
Partly a girl or woman, and partly something else.
A demigirl feels a partial connection to being a girl or a woman — real, but not the whole story. The rest might be nothing at all, or another gender, or something without a name.
It doesn't depend on assignment at birth. Someone AFAB might be a demigirl because womanhood only ever fit halfway; someone AMAB might be one because it fits halfway and that half is genuine.
The demi- prefix works the same way in demiboy, and it does useful work: it lets people say the connection is partial without having to claim it's absent.