t kind of sucks that the turtle just can't respect the fact of beauty and leave it alone.
Turtles arent humans and dont view life as rainbows and fairy dust.
Only humans view bettas as beautiful, every other creature sees them as little, deformed meals. Basically we have created bettas to be the easiest snack in the world. (brightly coloured, painfully slow, and stupid in regards to predators. Perfect for easy spotting and catching)
Im sure anyfish you put in there even the fast ones will live their lives in fear of being eaten by a giant predator...
Just get a new tank if you want bettas and tetras