Squandering Inheritance

IL - Irrevocable Trust - I suspect the trustee is working on not distributing funds for a beneficiary under squandering. The trustee has been vague when answering questions, not transparent or shared any information as to what is going on. The trustee has hinted at "legal action".

In order for the trustee to claim squandering, what must they prove? What is the process of that? How can the beneficiary being accused protect themselves? (Looking to get info while waiting for appt with lawyer)