I really do feel your pain. When my mom was alive she was a monster. That is not an overstatement either. She was an un-medicated bi-polar.
Time has brought peace and understanding, but at the time I just wanted my kids to be able to have a "normal" grandparent experience. Of course now I realize even that perspective was skewed. My grandparent experience was Grandma Nettie, who basically raised me.
When my kids were small I would take them to "Grammies" and she would proceed to feed them junk, take them to the store and LOSE them (!!) and show them tv shows that I specifically requested her not to because they caused the kids nightmares!! Gift indulgences were extreme, wasteful and plain old stupid. She bought
each kid a Casio electric piano one time when the oldest was 6. Explain to me why any household needs 3 electric pianos!!
She also seemed to take pride in calling up and getting a fight started between my hubby and myself. Don't EVEN try to go out in public with her. She would embarrass you to death.
It was our salvation that we laid down some VERY strict boundarys for her. It came to a point that the kids only saw her while we were with them. SURE she kicked and squealed, but when you aren't around to hear it - things are fine.
"I brought a bowl of GF soup and one of the ladies broke my bowl. I couldn't eat anything there so I went home hungry but we had a good time. "
I also really feel this pain. It is hard for others to understand how hard this situations is when everyone else is eating and there is nothing for you. We went to the lake a while back. We got in town late, missed lunch and just planned on going to the local restaurant before going to bed that night. All went according to plans and by the time I got to the restaurant I was STARVING. The
only thing on the menu that I could eat was a side salad which was lettuce and a half slice of tomato with no dressing! I nearly cried.
Keep doing what you know is right and everything will work out!
Rawrr!! 
