thanks for your question
Hoarding is one of important symptoms of Obsessvie compulsive disorder in a significant strata of population, compulsive hoarding is very anxiety
provoking to patient as well as to care givers. It is characterized by inability to discard items and individuals suffering from hoarding tend to store the items and they even some times do not let others to know this, due to fear of embarrassment. It is a part of OBSESSIVE COMPULSIVE
SPECTRUM disorder. Mostly the patients of hoarding also show other features of OC disorder like orderliness, cleanness, magical thinking, compulsive hand washing, obsession of doubt etc. In more than 50% of cases depression
is also associated. And in a few cases paranoid ideation may be seen as your friend is observing in his mother. It may be persecutory delusion
against any one or some times other delusional ideas like she is having. Her fixed firm belief about money is part of associated psychotic symptoms. In rare cases of Psyhcosis hoarding or obsessions or compulsions may be presenting symptoms thank frank delusions alone.
Best thing to resolve it is first of all try to reassure her, once she is ready to talk then try to give her evidence to contrary and see whether her belief is still fixed? If she is a little shakable and ready to accept that she might be wrong then further strengthen the evidence.
If thats not possible then take advise of some good psychiatrist
for further management of her psychotic symptoms
thanks, all the best
hope i solved your query