My Mum Has Been Feeling Very Lethargic These Past Few

My mum has been feeling very lethargic these past few days and has recently come out in a number of unexplained bruises on her legs. She frequently zones out when speaking to her and you can click your fingers and she has missed the whole conversation. She has a number of serious health complaints which she is being treated for and has recently come out of hospital after having some treatment for a kidney infection and kidney stones. What could be causing her lethargy and inability to pay attention?