Every time my grandmother talks to me (everyday since I live in their house for almost a year now) she brings up a sensitive topic. This situation has been going on for about 4 months now and I can’t stand it any longer and I know if I have to deal with this much more I will explode and I don’t want that to happen.
The topic is about the fact that I will get money from an estate that is currently getting sold. The reason this topic is sensitive to me is because I worked together with my stepmother to renovate the house and my grandmother hates her to death. She uses every chance to talk bad about her and in general spreads negativity whenever she can. E.g. "Why do you even try, she won’t give you your money anyway" or "You still help her? You are wasting your time!"
I tell her every time that it’s worth putting work into renovating an old house and I will get my money because my stepmother is not as evil as my grandmother thinks she is. Every time I try to tell her, she says I am such a naive fool. Still, she won't stop. It's not like she has Alzheimer’s or anything similar, but it seems she just loves to bring it up all the time. It has come to a point where I simply don't talk to her anymore until she bursts into my apartment/my room and I have to.
What can I say to her that stops her from bringing up this sensitive topic to me every time she talks to me although I tell her not to, because it worsens my mood?