Girl who I used to hookup with started hating me out of nowhere.

​

We ended things so that we could stay friends before it goes too far (same social group).

​

At first, it was fine. We talked, said hi as we passed, made jokes.

​

But now, she doesn't say anything to me at all and throws low jabs at me whenever we're in a group setting.

​

What's the possible reason for the sudden change?