Legal Question in Employment Law in California

There is no legal obligation of employers to treat employees fairly or well, just safely - as defined by Cal-OSHA, and to pay them in accordance with the wage and hour regulations applicable to their job classification and any agreed terms and conditions of employment - which may be verbal. There is no obligation to give any form of paid time off, whether sick leave, vacation, "PTO" or any other designation of paid time away from work (except in a few cities where local municipal codes require paid sick time for public health reasons). There is an obligation to provide what is promised or agreed, but there is no obligation to offer it in the first place. They are also free to change wages and any other terms and conditions of employment at any time, including adding or eliminating paid vacation policies, just not retroactively and not to pay below minimum wage. The director of a pre-school is almost certainly an exempt employee - meaning wage and hour rules do not apply as long as she made at least double minimum wage x 40hrs/wk. So you would have no claim based on the extensive hours she worked. As for vacation, you would have to prove that there was an agreement or policy about vacation that granted your mom vacation accrual. The fact that they offered to settle any vacation claim is not admissible evidence. So you need something more than that to prove there was actually an agreement, policy or terms of employment that she would get vacation. If you can prove that, with admissible evidence, then yes, the executor of her estate can proceed in probate court to recover the money as a debt owed to her estate. The estate would be entitled to all unpaid vacation, plus 30-days additional pay as a penalty.

Yes, theoretically, the representative of the Estate would have standing to bring suit for provable unpaid wages, plus any penalties. If she was a salaried exempt employee [likely], then she would not be owed any overtime as you seem to be thinking, and the Estate could only go after any paychecks she hadn't received at the time of her death. If that is the case, the Estate should make demand on the employer for that amount to be paid into the Estate.