SleepWhatSleep1 I'm sorry you are going through this. I would suggest you do your best to counter these arguments but not repeat them.
So don't say what she has said and then tell her it is wrong. Instead say
"Girls and women can study any subject they like, so can boys and men, Girls and women can do any job they like, so can boys and men."
Instead of repeating "Only boys can be doctors" and then saying that's rubbish just point out next time at your surgery, wow, 5 female doctors here. Nice men and women doctors here! Or whatever.
"There's also been talk about boys making comments about seeing the girls pants and commenting on their "fat" legs and tummies. I have made the teacher aware to pass on to the lunchtime supervisors." Well done.
If your dd says this to you ask her what she thinks, does it matter if someone tummy or leg is a bit bigger than someone else's? Of course.
Why do those people say it, is it to make people feel not very nice? If they want to make someone feel bad, then it's best to ignore them. But tell me and I will tell the teachers because mean comments are just mean!
"Her teacher denies all knowledge." Maybe her teacher doesn't hear what is going on. You could ask the TAs or the lunchtime supervisors.
In my dd's school there were boys who said they wanted to rape the girls! I bet the teachers never heard that either!
If I went to work and told my boss a colleague had something similar in my hearing I expect the last thing he or she would say is "Well I didn't hear it!"
Maybe she also wants to fit in at school, find the harmless things for her to fit in with but keep on with positive female messages.