I went grocery shopping with my mom last week.
Why did you have to go shopping?
Because my mom sent me out to do her shopping.
As she should, a mom should have a break sometimes with her chores. It is draining to do everything by herself and you wouldn't want her to get sick from stress or over exhaustion.
I will never forgive her for making me do the groceries chores.
I think you're over exaggerating. She asked you to do a favor. It's not a big deal compared to the many things she has done for you.