My f-bettas will actually swim around their tank HUNTING snails. The MTS however are better protected so I don't think I've actually lost a MTS to a betta.
Pond snails & ramhorns in my tanks will be yanked out and eaten within a few hours, but this is my betta. Yours may not not care as much.
I have pictures of this because I couldn't believe all the empty shells laying on the bottom. It's nice to know if I go on vacation I can just drop in a bunch of snails into the tank.