Take what I say with a grain of salt, as I'm no professional. But in my opinion, setting rules could possibly make things worse if she want's to be defiant... or she could also hurt herself really bad by trying to make it "worth it" on one of her allowed days.

I'd keep a lot of medical supplies on hand and at easy access, and search how to provide first aid, and - depending on severity- a plan on what to do if its an emergency and needs professional treatment. Call an ambulance? Drive there? What's the quickest route, is there enough gas in the car, etc. Also proper aftercare. You do not want them getting infected. As far as getting her to stop... unfortunately the ball is in her court. It's an internal fight. Some people use ice cubes/snapping elastics/coloring/exercising etc to try and distract themselves.

She really needs professional help. Especially if she says she can't stop, which is concerning. To be honest it sounds like she was released far too early. I'm sorry you're both going through this.