The old woman, as far as Shadow People go, is sometimes considered harmful. Her presence, for those who have seen, heard or felt her is definitely terrifying. People have reported being awakened in the middle of the night, to feelings of being pulled/forced out of their body.
Unfortunately, the study of this phenomenon is complicated by the fact that usually people who report such incidents are people who also suffer with certain sleep disorders or at least temporary and significant stressors and stress in their lives which are inhibiting proper sleep patterns and behavior.
Often, those who report this old woman/shadow person disturbance are suffering from SP=Sleep Paralysis, which happens when certain people are in highly stressed environments and moods. The condition is such that overly stressed people fall asleep from sheer exhaustion while their minds are still quite active. Some who suffer SP drop off to sleep while sort of in mid-thought with very active mental resources going on and it is as if the body just has to rest but the mind will not.
People suffering with SP may, indeed, awaken - with the mind active in a sort of very active dream state, except their body is trying to be in the sleep state and this causes the effect that a person cannot move. During normal sleep, the body's physiology is quite complex and a normal sleeping person is, indeed, paralyzed. If the body didn't physically and physiologically 'shut gears down' or induce a sort of paralysis, then every action we dreamed about, the body would attempt to do and then sleeping would be impossible for anyone.
Back to the topic of shadow people and the old woman...
Some who have had the above experience(s) report that they see shadows in a rather distinct shape of a woman...
I've still got to read more material specifically on "The Old Woman," because information on this topic keeps leading me to 'sleep deprivation' and 'sleep abnormalities' articles, which aren't telling me much about the cases of SP that might be considered paranormal events rather than physiological effects on the body of overly stressed persons.