OP the "for boys" thing has permeated everything she has done for the last 7 years. Like your school, her school split into boys and girls things very early in reception and left her quite isolated as she didn't understand why she was being left out of things with her friends. Obviously, it was driven by the mothers at that point but was very hard and we ended up moving her to a different school which wasn't like this at all and still isn't.
She does sometimes struggle with understanding that the boys don't always see her as 100% one of them. Her good friends do and the parties are often for "all the boys and sister sweet DD" but she's also invited to the all girls parties and I've often had to politely decline as she doesn't want to do hair & make up or karaoke.
We're now looking at secondary schools and have had to eliminate all the girls only schools which has given us a much smaller pool of schools to choose from.
However, as I said in an earlier post, we are seeing some changes in her and over the last 6 months she has started to build friendships with 3 or 4 girls in her class which I think is really important. Not because it normalises her at all, I love her male friends but because as she gets older and wants sleepovers etc it's much easier with girls. It's getting to the point where I'm not sure how much longer it's appropriate for her to have sleepovers with the boys.
All in all, keep going as you are. It is hard and unless you're in the thick of it you don't really understand. It's easy to say "oh let her do what she wants" and to a certain extent that true (she was the Spider-Man to the 20 princesses at every party for years) but equally, there is an element of you also needing to smooth the way for her not to become isolated.
I say all this assuming you're dealing with a child who likes boy things rather than one who is genuinely trans-gender.