Can I sue wrongful eviction?

I have rented a room since June of 09 and had no problems. Always paid my rent, kept quite, helped with the dogs. I don't know my states laws exactly pertaining to wrongful eviction. I live in Colorado. I pay $400 a month, utilities included. I was planning to move Dec 1st but I came home on Nov 15 and my landlord told me I had to vacate by the 21st and refusing to return my unused rent. She is saying she is justified in doing this since that morning I let my boyfriend of 4 months, who has stayed there many times and NEVER taking a thing, was there by himself sleeping for a while. I had to go to work and it was his day off so I told him to sleep and to take my key and lock up when he left. Is this legal even though I'm paid up through Nov? Can I sue her for wrongful eviction and if so how much can I reasonably expect to get?