Legal Question in Real Estate Law in California

I'm sorry your niece hung herself. You didn't say what arrangements you had with the "friend," whether you had anything in writing, or whether you paid her anything. In the absence of a written agreement or payment, and the ability to prove in court what stuff you had, yours is an improbable lawsuit. I'm not saying this is you, but we get lots of mail from people whose friends impose on them as if they were a self-storage business. I have a feeling there is a lot more to this story that you're telling us.