Sweet of you to want to help your mom out that way.
I had my gallbladder removed a couple years ago, I think I was 48, and I did so well I was begging to go home the same day. I hope your mom has a similar experience.
Once I was allowed to eat I was able to eat anything, but since your mom is diabetic I would think a controlled carb diet would be in order. Lean meat, veggies or salad and something whole grain, perhaps?