Frankenstein's monster was male and specifically asked for a female bride, it's an integral part of the story. If Frankenstein's monster asked for a non-binary partner, that too would be an integral part of the story and I would have used non-binary instead of female.

The entire film is predicated on a female Frankenstein's monster and from what I now understand, lots of feminist themes.

If this were a parody of a Disney Princess movie and it was predicated on a male lead, I'd have to use the same language but you wouldn't flip out.

I understand what you're trying to get at, but I don't think this is a spot to make a stand on gender language norms and the word "female" being sexist. There are times when it is, but this isn't that time.