Don't walk her so much that she gets tired. If she starts pawing her tummy or tries to lay down then walk a little bit. Just DON'T let her roll. She could twist her intestines from rolling and that can kill her.
I'm new here & wanted to add on my two cents for what it's worth- my friend went through this situation just the other week & the horse had the exact same symptoms as your horse. I don't want to frighten you, but the horse ended up needing to be put down. We both thought it was choke just the same as everyone here but it ended up being impaction colic I think. Regardless it is my opinion that the vet needs to get out there pronto.