A grandchild moved into my mothers house and has destroyed the backyard with no consent from my mother, the owner of home.

I am the Power of Attorney for my mother and there has been an ongoing problem with the grandchild living in my mothers home. No permission was granted to completely strip the backyard to dirt. The current status is 90% dirt where a beautiful patio used to be with flower gardens and trees. The grandchild took it upon herself to do destroy the once beautiful backyard. The house was built in 1952. The grandchild was asked to inform my mother of any work done to the house to be approved by her or I and she ignores it. She is very bossy and just tells my mother what is going to happen. My mother wants them to leave her home, but the backyard is in an uproar!! She threatens my mother that "she will see her in court" leaving my mother overwhelm. There is more to this bad situation but it boils down to Elderly Abuse at every angle. What can be done on my part? Thank you for your time.