Why does my friend have such bad breath?

I have a friend who I’ve seen brushing her teeth many times! But her breath is sooo bad that I have to stand at least 2 feet away from her. I’m slightly considering the possibility that it’s because she’s a vegetarian, only because I’ve met 4 other veggies that also had bad breath.

Maybe it’s something else though. Could it be what she eats, or could it be something else?