You wrote >she is merely a guest in this house< she is not just a guest , she has PAID RENT to live there and if she has been there more than a month she has established a tenancy even if its due to her paying the two of you and not the landlord and so your crystal clear on this if you don't follow your states laws with this rental relationship you and other on the lease roommate created by accepting rent money from her , she can treat you just like a landlord should you constructively evict her by driving her out or cutting off utilities or any thing else that meets what your state defines as a illegal eviction / self help eviction It wont be your LL that gets sued for violating the law .