Your father-in-law has Alzheimer's and his wife, who is in failing health, cannot take care of him. However, she continues to dismiss any in-home help you hire.

You have a very difficult situation. The fact that your mother-in-law keeps discharging care providers makes it doubly difficult. The ultimate decision may be to move your father-in-law into a skilled nursing facility or Alzheimer's' wing of a facility. Since you want to be able to direct the care of your father-in-law, you will either need to be his agent under a power of attorney or his guardian/conservator. If he has not designated your husband as his agent under a power of attorney, then you may have to file for a guardianship/conservatorship to control. If he has designated his spouse as the agent under a power of attorney (and your husband is the successor), then you must convince her to resign. If she does not want to resign, then you are in court. I am sorry that the choices you have to make during this difficult time, but your options are a bit limited is the spouse does not want to cooperate.