I disagree on that one. Josy told the MC that she was in a relationship, which was the important thing. The fact that her significant other was a girl should not have mattered (unless the MC was after her girlfriend as well, which would be on him, not her).Which bothers me a bit. I can forgive Maya for her hidden truths, coming from a family where your own fathers turns against you is simply horrifying, Josy on the other hand... nope. She could have told the MC way more than she gave him.
If anything you could argue that Maya and Josy did a poor job of communicating with each other (apparently Maya didn't tell her girlfriend that she was sharing her dorm room with a guy), but considering they agreed to keep their relationship a secret, I'd say it would have actually been a dick move by Josy to reveal her girlfriend's name to the MC for no apparent reason.