Ha-ha! Thanks, folks! I'll give a try once again tomorrow to the same mouthpiece as my eggbutt to see how she'll do. If it won't work I'll just stay with eggbutt.
The problem with it is that my trainer says she can go "behind the bit" (not quite sure what it is), and that's she doesn't chew on eggbutt enough to show relaxation. But I think it's confusing, because she doesn't look unhappy or anything. Well, I don't know...