No LL in CA can evict you. Only a CA court can evict you. A CA court will only evict you if there are legal grounds to do so. Your rights and responsibilities will be outlined in youre lease agreement.
What the LL 'says' if not in our lease, likely is unenforcable.
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She may want to evict you but it does not mean she can evict you. My impression from your question is that you lived there in the past and returned in October. It will depend on what the terms of the new lease are. If she has a new written lease, signed by you and which states you cannot use the yard, and she initiates an Unlawful Detainer action upon finding out you were using the yard, she can probably succeed against you.
However, if you are on an oral lease that does not exclude access to the yard, you can prove she knew you have been using the yard the whole time, and she has accepted your rent each month, then you have a better chance of successfully defending.
If your landlord insists on moving forward with an unlawful detainer you should get an attorney.
Best of luck.