Hello Erin,
I really feel for you even though I am the other side of the pond, as it were. You don’t say how old your mum is. Mine was 90 when she came to live with me and my husband. She was often my trigger, and had this sort of grunting noise whenever we ate together. I would ask her why she was grunting, but she would call it breathing. It used to drive me mad! I think it is perfectly ok to walk away from a situation that triggers negative reactions in you as a person, even if you make some excuse as to why you might be leaving the room. Sadly, my mum died last month and, in a way, I feel as though I would put up with any amount of grunting just to have her back. But I hope you find a way through your situation and manage to come to some kind of happy compromise. Wishing you well, Sarah