My sister was sleeping last only to wake up and have an unseen force hold her down in bed. She couldn't move or say anything. We are confused as to what it could be.

Sounds like sleep paralisis I've had it happen to me over 100 times in my life no serious cause for alarm. Was she sleeping ,but when she woke up she was conscious as if she was awake ,but couldn't move as if she was asleep?

P.S be sensitive sleep paralisis is deathly scarry to someone who's not used to it.

Gamed
Yes, she told me she was awake but couldn't move and was fully aware. I don't want to jump to any conclusions but I shall speak with her about the sleep paralysis. She fears it's demons or an evil presence, I believe it could be but try to change the subject as to not frighten her.
Thank you for taking the time to reply, much appreciated.

No problem by the way sleep paralisis is very common over 50% of people will experience it at least once in a lifetime. It basically is were you as a person have woken up but your body is still in rem sleep or not aware that you have woken up. If you need help on how to prevent this or advice I'm always here.

Sleep paralisis is very very common, has happened to me on a couple occasions.