Replying to Somebody borrowed something of mine and won't give it back, what's the move?

I let a friend of mine borrow a dab rig about a month ago, I told her she could use it for two weeks. Two weeks ago I sent her a message asking for it back, didn't even open it. I've been sending a message every 3-4 days and she is purposefully not opening them. I've decided that this is absolute bullshit :)

What course of action do I take now? I'm currently planning on waiting till Monday and than messaging her saying if I don't get it in the next two weeks you're going to regret it. If I don't get it in those two weeks I'm going to pull some fuck shit.

Ok so basically I'm fucking pissed and I don't think I'm thinking very clear headed. NS what's the move here?