There were a handful of female students in my physics program, on a per class basis it would be like less than 10%. There were a few girls that took the 4th year General Relativity course which ironically wasn't a requisite in our cirriculum (I didn't even take it myself meaning I never learn GR with my BSc but I know a bit about Quantum Computation). Although I don't recall any girl taking abstract algebra classes like Group Theory or Field Theory. Overall I think about 5-6 graduated in my year.
Then again you can have Winnie Cooper in your mathematics program, she even has an Erdos number!