Legal Question in Real Estate Law in California

Probably none. Based on your version of the facts, this was a gift. I'd have to hear (or read) her version to give a really sound opinion as to whether she could make a case in court that there was some kind of understanding to the contrary, entitling her to recover part or all of her outlay.

I agree with Mr. Whipple that she "PROBABLY" has none. However in the absence of any written agreement you will be facing a "he said, she said" situation. The good faith improver law would not help her, since there was no mistake she did not own the property. She could probably plead something that would get past the demurrer stage, but without knowing her side of the story I can't see much of a case she could win.