Now my ex-girlfriend stabbed me in the arm with a steak knife after I had minor surgery to "check if it was numb."

For context: I'm 16 (m), my ex is 16 (f), and we dated for about 5 months. When I had minor surgery on my hand, they gave me some painkillers. When she came to my house, she decided to stab me in the arm with my family's steak knife to "see if it was numb." By the way, no, it wasn't. She said I was a "baby" and that she didn't even stab me that hard, although the knife went in deep enough to require stitches. Afterwards, she reluctantly apologized, and for some reason, I decided not to dump her on the spot. Long story short: she's a terrible person, and I should have left her much sooner.

Update: She just got sent to juvenile detention for trying to set her new boyfriend's house on fire. Guess I dodged a bullet.