It's okay to state that you wouldnt keep her son from her. But you might consider following up that sentence with a dose of reality next time....".....unless there is a reason for me to be concerned for his safety..."
The seat belt incident oughta slap her right upside the head if you were to say that. It has to be stated matter of factly though. Not with condemnation. She'll HEAR condemnation and judgment but that's her problem to deal with. Don't shelter her from reality. Keep it simple but state facts.
Word of caution: Don't expect her to wake up the first time you try this. It could take many times and even still, it may NEVER wake her up. It's still your best tactic in my opinion though because it will keep the guilt monster off your back - and believe me, it will always be sniffing around YOUR door even if it doesn't seem to so much as give her a passing glance.
"Let anyone who thinks he stands take heed lest he fall" 1 Cor. 10:12
