Chops, that is a problem!
My rule has always been, unless everyone is buckled up, we don’t move – no matter if a little one was crying, whining, screaming, or complaining. And believe me, it has not always been easy to do, especially when we are running late! But I have never had to deal with your problem.
How old is she? Is she old enough to understand that you will pull over each time she gets out of her car seat? If Mommy is not driving, then we can’t get to the store, playgroup, or wherever you are going. This might be difficult at first and you’ll need to leave yourself extra time to get anywhere. But if she’s old enough to learn how the release mechanism works on her car seat, I have a feeling she could understand this cause and effect.
Hatzlochoh!