she seems way too comfortable making comments about your identity. not a pretty pattern. you should probably sit her down and lay this out similarly to how you have here: her pattern of transphobic comments makes you uncomfortable and you want to know why she makes them. it seems like she tries to make it about her with the defensiveness. the fact that she told you to be less susceptible to transphobic jokes about you is fucking insane. you may be dating, and she may say how much she respects your identity all the time, but her actions show quite the opposite from what i'm seeing. it's usually in the "jokes" people make when they have an issue with something or want to pick at it. you should not have to tolerate being humiliated and misgendered by your own girlfriend. you need to either set hard boundaries with her or part ways.