Dr pepper- mezuzos in the worng place isok to say! The parent is allowed to point out something which the son/daughter obviously doesn’t know or realize.
But when the child knows what he’s doing(like not going to shul, or even wearing a blue shirt instead of white:)….) Then it is SO WRONG for the parent to tell something.
I’ve had my experiences when my hubs or my parents pointed out certain(real dumb) things and what should I tell you…it didn’t do too good.
If you marry off your child, you gotta trust him/her that they know how to go about their own lives. Even if they don’t do 100% as you want.