The California Family Rights Act (CFRA) provides leave to care for family members not covered by the Family and Medical Leave Act (FMLA), including grandparents, grandchildren, siblings, parents-in-law and “designated persons,” who are individuals “related by blood or whose association with the employee is the equivalent of a family relationship” and whom the employee designates at the time the employee requests leave. Therefore, even though your employee has already used 12 weeks of FMLA/CFRA last year to care for their mother, they're entitled to request CFRA leave now for the care of their grandchild.
Whether they're entitled to that additional time depends on their eligibility for the leave (that is, having worked 1,250 hours during the 12 months prior to the leave).
If they were not full time and had missed a lot of work during that time, they may not have worked enough hours to qualify for the leave. Time worked includes regular and overtime hours, but not paid time off (PTO) hours, such as sick, vacation, PTO or holidays.
While CFRA leave may not be available to the employee, the employer should check their employee handbook and past practices to see if they have provided employees with a personal leave or unpaid time off.
A personal leave, while not required by law, is used often to deal with short-term personal or family issues that prevent an employee from working. Just be aware that what you do for one employee you would be required to do for others similarly situated to prevent discrimination issues. It is up to an employer to decide whether those accommodations can be made.
Note: The CFRA provisions relating to care for family members require that the child have a serious medical condition and do not cover situations where child care is not available. On that basis, the CFRA request could be denied.
Read more about CFRA and FMLA Employer Coverage in the HR Library.