I recently started dating this guy and his ex won't leave him alone. She's came over to his house and asked him to cheat on me with her. She got pissed before too and stabbed him with a fork. She even took his phone and texted "I'm dumping you." to me!
Is this normal?!?
Is this normal?!?

Insanity isn't.
If I were you, I'd knock her out, tie her up, put her in a sack, tie the sack closed, put the sack in a chest, add some heavy weights, lock the chest, and drop it somewhere in the middle of the ocean.
Or just punch her in the face. Whatever capsizes your fail boat.