The first thing you have to do is look at the rental agreement. You stated that you mother has rented this property for over ten years. A lot of times when a person rents for this long in the same property they feel they will stay forever and do not sign a yearly rental agreement. Therefore leaving themselves open to the State or municipal laws. Since every state is different you really need to contact an attorney if you can not get the problem worked out with the landlord.
For residential leases the landlord must provide sixty (60) days written notice to terminate any periodic tenancy, if all tenants and residents have been in the property for at least one year (Cal. Civ. Code Â§ 1946.1(a) and (b)).
Best Regards, Jeff
If the tenants are only month to month landlord MIGHT have right to provide 90 day notice. If landlord is within the rights of 90 day notice following agreement per the terms, if tenants stay eviction, locks, damages to landlord, can be allot of drama involved COULD be NOT TO FAVOR of tenants.
Confer with attorney review executed agreement tenant rights