Durable Power of Attorney My mother in law has a Durable Power of Attorney for…

Durable Power of Attorney
My mother in law has a Durable Power of Attorney for a wealthy aunt with no children and no relatives living close. The aunt resides in a nursing home, she has dementia. My mother in law has very little money and a worn out automobile. She is on call 24/7 since she is the only one around to do everything, actually the others have been of no help what so ever. Can she legally trade in her car and purchase a fairly inexpensive car and pay payments with the aunts money as long as the aunt is alive and my mother in law is the sole caretaker? I see no reason for my mother in law to continue to wear out what is left of her car to continue to take care of someone who is wealthy. There is no compensation for my mother in law and there isn’t any specified in the Durable Power of Attorney. What would you suggest? Thanks for your assistance.–name removed–