Do you think she maybe gets a little car-sick? I know as a kid I had motion sickness that made me loathe long car trips, especially if I wasn't next to the window. For the trip home maybe try putting her near the window (if she's not already), or try the sea-sickness bands you can get from a chemist. Make sure you take plenty of breaks so she (and you) can calm down - even if it makes the trip longer, doing a 3hr drive in one go is way harder than doing 3 1hr drives broken up by short play-breaks.