Legal Question in Real Estate Law in California

Yes. The two of you need to negotiate for one of you to buy the other out, or the property must be sold. If you cannot do one or the other by agreement, one of you must file an action for partition. Then the courts will either award it to one of you with a buy-out of the other, or will order it sold. If it is not sold by you or the court, the one who keeps it must refinance the mortgage too.

I would need more factual information. Mr. McCormick assumes a lot of information without you providing it. He assumes that you are either joint tenants, or tenants in common, and that she is going to sue you for partition. She can't sue you for not paying the mortgage, unless you have some sort of agreement in place. You would have to let us know who was on title, and who signed the promissory note. You may be personally liable on the note, even though you may not be on title.

Of course. Anybody can sue anybody for anything. You appear to have a legal interest in the house. You could sue for partition and sale of the house, if there is any equity in it to make that practical. The bank could go after both of you in the event of foreclosure, depending upon the nature of the loan.