In Texas, can a non-parental parent leave the State in the middle of a custody battle.?

My Son has legal physical custody of his 2 children and is in the middle of a "horrible" custody battle. The Mother is mentally ill and is her own attorney. The Judge has ordered her to have a Psychiatric Eval for the court within the next 60 days. Upon returning to the court with the Evaluation she has to begin paying child support. She has bought a bus ticket and is leaving the state (saying she is going to go to Az to visit and to help her sister). This is an excuse to not get her Evaluation again. What happens when we appear at our next hearing and she is not there?? We have no set date for this hearing yet. Does it just go "on-hold" ?? She has not let the Court know of her plans. Thanks for any input.