Does my grandmother have a mental problem?

My grandmother is 86. She had a paralytic stroke three years ago and lost her speech. She can only move the left side of her body. My grandpa (her husband) had been diagnosed with dementia with psychotic features. a month ago, he fell down and ended up getting a brain hemorrhage. He doesn't have any idea where he is half of the time. The reason I mention this is because he even forgets her name and who she is most of the time and they've been together 66 years. she cries a lot of the time. generally, she's quite alert. however, for the past few weeks, she keeps pointing to my father's pockets and tries to take out money from it. if she does get a hold of some and we try and take it back, she snatches it away. it come to a point where she hides it under pillows and i've seen her do similar things with her hair elastics. whenever, they break she refuses to let go of them, she holds them in her hand and if anyone takes it away, she snatches it back. she also has a tendency to get really hysterical about the money at times. she absolutely refuses to give it to anyone. it's becoming very weird. is this a mental problem or does my grandpa just have a thing for money and elastics?