You likely have a Sub-Tenant. As such if you have asked her to leave and she has not then you'll need to proceed through the eviction process. The first step is to provide legally sufficient notice. If you are not familiar with the eviction process I recommend that you contact the Robinson and Henry eviction team for a free case assessment by calling 303-688-0944 or scheduling online at robandhen.wpengine.com/locations. You want to do this right the first time as you do not want to have to live with your roommate through the process twice!