My question involves an eviction in the state of: Washington State

This is a complicated situation, at least I think it is. I own my own mobile home in a park. Last November, my (now ex-) boyfriend was living with me and asked if his friend (and her son and boyfriend) could stay with us for a while. I'm a very nice person (sometimes TOO nice!), so I said okay. Well, she moved in an entire household worth of stuff, into my bedroom, shed, and front deck. Things were okay for a couple of weeks, until some of my neighbors made complaints against this girl's boyfriend (speeding and loud music in his car). The girl and her boyfriend both got notices to leave immediately (they had 72 hours to vacate) or they would be arrested for trespassing. I was understanding of my landlord's side, but I was also understanding of this girl's side. BTW, let's call the girl 'Katie'. Katie was going to have to couch surf, so I agreed to let her leave most of her stuff at my house. I even told her that she could leave it until she found a place, which I thought would be just a few months. Well, I found out on Christmas that my mom was moving in with me at the end of January. I let Katie know in the beginning of January that she needed to get her stuff out before my mom moved it, but Katie let me know that she had a warrant for her arrest, so she was turning herself in any day, and would be in jail for the rest of the month. I've told her multiple times since then that she NEEDS to get her stuff out. Now, I'm needing to sell my house, but I can't list it with all of her stuff here, because it's so crowded that nobody could really see some things that need repairs, and my bedroom floor is falling apart because of water damage, and I can't fix it because she still has a bunch of furniture in there. I don't have an address to send any legal letters to her, and she keeps saying that she is moving into a place, but it's been weeks of excuses and I'm needing her stuff out ASAP. What are my legal options? She was only here for 2 weeks, and wasn't on any kind of lease or written agreement.