Can my roommate really not pay me?

So I recently let a young girl and her baby live with us. I felt bad that she was practically homeless with a daughter around the same age as mine. I let her move in free for 2 weeks. She was originally supposed to pay 400 but I dropped it to 350 just to be nice. Well we had a horrible experience with her living here. I guess its cause shes young but we couldn't handle it so her 30 day notice was coming on the first of the month. I just feel like I've been so used by this girl. Well anyways she decided to move with her bf on the 20th. I was all for that but I told her we need a 30 day notice. She was fine with that and left her bed here so when she paid she could have it. Well she just text me asking if she can move back in. I told her that I would have to talk to my husband first. I also told her that I moved my kids into her old room because it was to hot having 4 people in one room. So basically she flipped out on me saying she's not going to pay the rent she owes me. I told her you can come till your 30 days are up but she probably wont be able to stay after that. So my question is there any legal action I can do in order to get the rent? If I don't get this rent we will lose our place to live and I don't have any family so we will be in a very bad situation. My husband was recently laid off I'm so nervous right now. There has to be something I can do right?