Legal Question in Real Estate Law in California

Yes; the essence of a "month to month" rental is just that; it is an arrangement that is valid and enforceable be either party on a month-to-month basis. A recent law change extended the notice period from 30 days to 60 days for tenants who have been there more than 12 months, but otherwise a month-to-month tenancy is terminable by either party on 30 days' notice.

Mr. Whipple is entirely correct [the major disadvantage of renting is that you can be force to move, sometimes without any reasons], but check to see if your area is cover by any rent control/vacancy decontrol rules. The go to the landlady and try to smooth it over, pointing out that you have always paid your rent on time, have not caused trouble, there likely will be a 2-4 week gap before she can re-rent, and does she really thing she will find tenants who overall are as good as you [none of which will work if any one factor is untrue].