Maybe if you had a spare booster seat to loan her to could open the conversation that way saying xxxx mentioned you forgot the coarsest in a friends car I have one here for you to borrow as I wouldn't want anything to happen to her or you to get a ticket ."
Dido that's all I would do. The chidhood could have also been misinformed, my D.D gets upset if we don't use her favorite car seat and she has 3.