beneficiary signed away rights to estate, now trustee not following written agreement

My father died many years ago. My mother was the beneficiary of his estate (the income, and principal if necessary), My mother has her own estate and has never needed the principal of this estate. I am the beneficiary upon her death, at which time the trust is terminated and disributed to me, free of trust. My question is this: I am in my mid-forties. If my mom had died ten years ago, the trust states that it would have terminated when I turned thirty five. My mom and I discussed this and she agreed to denounce her interest in full as the beneficiary, thus terminating the estate at this time and having it revert to me in full, free of trust. The trust does not penalize for early termination and allows for this disclaimer. My mother and I both signed the intent letter and forwarded it to the trustee of the estate. MY QUESTION: Isn't the trustee mandated to follow the wishes of the beneficiaries, impartially? By signing that document, aren't I the current sole beneficiary of the trust? My mother's attorney appears to be attempting to delay this process. He is her attorney for HER estate, but this was my father's estate, and quite small in comparison to hers. What rights do I have to complete the termination of this estate? My family's well-being is in question and the monies are of an emergent nature.