Define biological female.
Of the sex that normally produces large immobile gametes.
It isn't clear to me that a definition that includes the word "normally" is effective in a context that involves an uncommon subset of persons.
For example, suppose we were having a discussion about a lesbian teenager. Someone writes, "define female." and you respond with "of the sex that is normally attracted to males." That isn't at all effective in context.
Now perhaps you could change the wording of your definition and it could be more effective. I don't know. I'm not over-analyzing it. Or perhaps you could try again.
As far as I am concerned, when people say "sex is binary," I think they are wrong and when people say that sex is fluid I think that is also an over-simplifcation. To me, and I could be wrong, sex has multi-dimensional characteristics, not merely one, and some of these characteristics may be fluid, binary, or bimodal, but overall, I think that sex is bimodal.