My mother and I are both diabetics just like you and your mother. My mother and I have a very tumultuous relationship for several reasons that I won't go through here.
Let me tell you something...If family is not serving your best interest than leave them alone and find people that will care for you. I have stopped trying to be the apple of everybody's eye just to please folks. Ultimately it was me that went home sad and these so called family members never called to ask how I was doing.
I would try to talk to my mother about her diabetes because I knew my sisters won't do it. She tries to duck the truth that her numbers are always over 300. I am glad you are able to have a common ground with your mother.