So she's lied about who she has been talking to, deleted messages etc and is now trying to accuse you of something you haven't done.

Why are you apologising when you know you didn't do anything wrong?

Either she's incredibly insecure and controlling or she is up to no good again and is trying to gain some moral superiority

Either way she sounds like a massive red flag. Do you really need this crap when you're only 22

Bin her off and concentrate on your engineering degree