Welcome to Health Care Magic,
Though you have not given details about the cause of pain, and type of cancer, generally speaking it is not advisable to take Xnax and fentany patch together. Also to increase the dose of Fentanyl
abruptly is not a wise option. Make sure also that she is not taking grape fruits or Grape fruit juice along with these medicines.
It is advisable to consult her Doctor who can review her cause of pain, may revise the timings and doses or choose an alternative option for the pain.
Wish her good recovery.
Dr H Hamdani