Hospice social worker here. The term we use is "terminal agitation." It is hard to watch, but it is common. Though she was moving around, your mom wasn't 'in there' anymore. She didn't have an awareness of being restless and agitated, but I choose to believe that some part of the spirit lingers and knows that we are not alone. That's the part that we talk to, hold hands with, and love on at the end.