I learned my girlfriend [F] has a naughty account on Reddit she doesn’t think I know about

I’ve been using her computer for work and when I went to check Reddit, she was signed into her account.

She’s posted photos of herself and has dozens of messages with strangers where she’s sexting with them.

It’s very clear on her page that she has a boyfriend…and she mentions me constantly in a “I’m clueless way”. She also constantly makes fun of my penis size to any man who sends her a dick pic.

It’s frustrating, humiliating and I’m not sure how to confront her.