She is apparently suffering from a sleep disorder called
REM sleep disorder.
A complete
sleep cycle has two stages:-
1. NREM (Non
Rapid eye movement) sleep:- It is the first stage of sleep, which accounts for initial 75 minutes.
2. REM (Rapid eye movement) sleep:- It is the second stage which occurs for later 25 minutes.
In REM sleep disorder a persons experience a vivid fearful dream and suddenly wakes up from sleep. During REM our body is generally relaxed and flaccid. But due to disorder of REM sleep person's body becomes stiff, muscle may gain power and person can act like shout, scream, or move limbs also.
Hallucinations soon after awakening are a known phenomenon and are called as hypnopompic hallucinations.
So your relative is having REM sleep disorder causing sudden awakening at night followed by hypnopompic hallucinations of hearing strange voices for some time.
The treatment is possible and there are good drugs that can cure this illness.
I suggest you to
consult a psychiatrist who may asses her in detail and prescribe her few psychotropic medicines like melatonin, ramelteon or clonazepam.
I hope it answers your question. I wish her a better health.