Legal Question in Wills and Trusts in California

The estate belongs to her children, 50-50. That is called intestate distribution. There is nothing you can do, unless the children in which case a court will appoint guardians ad litem.

The only possible step you could take is to have an administrator appointed to the estate, who can essentially referee the dispute between the two children. This, however, is often a thankless job, and it is not clear that the court would favor you as the administrator as opposed to one or both of the daughters.