Can a trustee, in California, not named as a beneficiary deplete the principal of the trust by making payments to themselves?

17 years ago after the death of my father, the trust attorney sent a letter to my sisters and myself stating that we were not entitled to an annual accounting, of the irrevocable side "A" of my fathers trust. Now that my step-mother has passed, we were advised that the trust principal is gone. I have asked for an accounting but the attorney is not responding to my requests. My step-mother was to receive the interest from the "A" side principal but was not a named beneficiary to the "A" side. Is there any way to hold the attorney accountable as it is my belief that if an accounting was done the principal would have been secured and my step-mother would have had a tidy income until her death. Her last payout was less than $100.