one of mine seem to like nothing better than chasing them down and removing their eyes for a tasty snack but some bettas may not be so ruthless.
I've also had snails harrassed to death by my bettas so not much is kept with them now but as they are all different it won't hurt to try but perhaps only put one shrimp in there at a time to guage the bettas reaction.The shrimp that my betta picked the eyes off was an adult ghost shrimp, I think what attracted it was it's darker eyes, they were kind of the same size as the betta pellets I feedI've also had snails harrassed to death by my bettas so not much is kept with them now but as they are all different it won't hurt to try but perhaps only put one shrimp in there at a time to guage the bettas reaction.