Either the tenant/roommate bought the house with her and this is why they aren’t being evicted to find a new roommate, or she bought the house with someone else (possibly a now-ex) and had to take in a roommate to be able to pay the bills after a split. I had a coworker once who was married a very short period of time and kept the house in the divorce, and then used the extra rooms in the house to rent/airbnb. She planned to ramp this up until she could stop working, which seemed like an odd plan to me, but alright.