So I just googled demigirl and it led me to this page on nonbinary.org which has a better definition that the one I gave

“A demigirl is someone who only partially (not wholly) identifies as a girl or woman, whatever their biological sex”

“demigirl can be used to describe someone assigned female at birth who feels but the barest association with that identification”

“or someone assigned male at birth who is trans feminine but not wholly binary-identified, so that they feel more strongly associated with “female” than “male,” socially or physically, but not strongly enough to justify an absolute self-identification as “woman”“