I also suffer from recurring sleep paralysis. I am not too religious but I found out that they are demonic possessions so I decided to test this...
During an episode when I felt the presence entering I said "Jesus please protect me and keep me safe" and I only had to say it 3 times (well I know during SP it's impossible to speak but I was thinking it and it was like my thoughts were coming out loud) anyway after I had said this I heard a piercing screeching sound coming from behind me, I felt something push me and I started feeling vibrations and I woke up. When I had woke up the screeching sounds were still ringing in my ears. It was a terrifying experience but I at least know what to do to stop an episode instantly. And also they want you to be scared, so saying that really does turn the tables. But anyway even if you just say Jesus, it will help! Believe me. I hope your Mother get's better, I know what it's like! Good luck!!