Purpura - spots on the face?

My 95 year old mother with dementia wakes up with small patches of purple splotches on the sides of her face and neck. I have researched it and the only explanation is “picking” or “pinching” the skin on neck and face in her sleep. Could it be a nervous disorder? Most elderly people get these splotches when they bump their arms. The spots eventually fade but she does it again and again. They look like dark flat blood blisters. I don’t know how to stop her from doing this to herself and she says she doesn’t know how they happen. I tried putting the nighttime gloves on that keep her hands from going to sleep but she pulls the gloves off. Every day she looks like she’s been in a fight. Anyone have a clue what can be done? She does take anxiety meds.
Charlotte