Are Benadryl Tablets Known To Help With Pain?

My 73 year old mother is taking 12 Benadryl tablets every day. She says she has allergies and has to take them. Some times she says she takes them because of the pain , I tell her that Benadryl does nothing for pain. Sometimes she says that she takes them to get rid of fluid buildup, I told her that I researched it at the Benadryl site and it does nothing for fluid buildup. She gets angry. She said her doctor said she could take this dosage. I told her that I do not believe that her doctor ok d her taking that many Benadryl pills every day of every month. I told her that I think she is taking them for the sedating effect. I think that this has been going on for at least two years. She gets very angry if I refuse to buy benadryl for her when I do her grocery shopping. I just found out today how many pills she is taking every day. Is there a problem with her taking this many of these pills every day?