Mom is having extreme nightmares?

Ok so my mom used to have nightmares almost evry night. She would scream while asleep and i would come running to wake her up. This stopped for a while but now shes starting again and its getting worse. now its evryday and her screams are super loud. Most of the time shes yelling 'help!' but shes also yelled out 'murderer' a few times. I always wake her up and when i ask her what she was dreaming shes half asleep and cant really talk. When i ask her the following morning she says she cant remember...whats wrong with her? Trauma? Subconscious? What can we do to make the nightmares stop? i ask her the following morning she says she cant remember...whats wrong with her? Trauma? Subconscious? What can we do to make the nightmares stop?