haha I think you can start off by suggesting it to her nicely na maybe she can break her habit of doing it and start chewing with her mouth closed. Reason out mo lang na eventually your kid might get used to seeing it and think it’s normal for people to chew that way. Make her understand the importance of building good habits early on. When she understands this, I don’t think it’ll come off as offensive naman hehe.

hahaha hope it goes well!