Good story. It's hard to say, not being in the situation. I think you are being considerate and taking her better acts into account, such as birthday card. On the other hand she seems to be disrespectful to other tenants there and making noise, and leaving a mess. Seems to be both at odds - respecting your BD but not your space or home. It's your home too. I would not confront her too openly. Maybe ask her friend how long she plans to stay and ask she cleans up after herself. Problem is if there are no rules, you may have to make them. The lack of contract and rules is something she could exploit.