How long has this been happening? Any recent hospitalizations, new medication ,etc. A sleep study might be a good idea once you rule out any infections
If this is a case of very realistic hallucinations, very elaborate, and occurring often at night hours, this is a early symptom of Lewy's. This is something to check out with Mom's doc who will run some basic tests (draw a clock set at a specific time; spell a word backwards, and etc) and will decide if further neruo-psyc testing is needed.
lyunek, have your Mom be tested for an urinary tract infection [UTI] as such an infection is common in elders, and can produce a whole variety of different symptoms, even confusion. This type of infection can be controlled with antibiotics.
Some medications can cause really lucid dreams and/or can cause a deep sleep that it can be difficult to wake fully from for several hours after arising, have you investigated that?
This is something to check out with Mom's doc who will run some basic tests (draw a clock set at a specific time; spell a word backwards, and etc) and will decide if further neruo-psyc testing is needed.