I want to ask my wife to eat her breakfast a certain way
What is the issue you have with the way she eats?
She eats like a slob. Always chewing with her mouth open.
You should try to encourage good table manners. You should say it nice because she might be offended and could get angry with you.
I'll try to talk to her nicely about it.
That's good. Just say things like, ''Honey, can you close your mouth when you eat?''.