Legal Question in Real Estate Law in California

Yes

Whoa! I'm not so sure that she can. If you have been living there for 30 years and have paid all the taxes, you may have a case for adverse possession. You may have a case based on the principle of equitable estoppel, as in the landmark California Supreme Court case of Monarco v. Lo Greco. What kind of an agreement did you have? It doesn't necessarily have to be in writing nor does it even really need to have been spelled out in full orally. Courts often can tailor legal judgments to give the parties a fair and just result even when there have been some omissions to carry out technical details on paper. I'm not saying you have a perfect case, or even a solid one, but on the other hand, you might well have defenses to an eviction attempt.