Let the administrator know a few months before your mother's funds are depleted. The facility may be willing to negotiate to a solution. If your mother has not already qualified for MediCal, you should file an application for her. If she qualifies and receives SSI, the facility cannot evict her.
Your mother may have to move into a skilled nursing facility. Ask her physician to assess if she needs that level of care. Also check what facilities your mother's doctor visits. The best way to determine if a facility will work for your mother is to visit it personally.