Hmmm, do you think you could give her a really good booby feed before you leave and then try to tide her over with some EBM (not sure how you're going with that though - she wouldn't take a bottle would she?) so that you get a bit longer before stopping and giving her another *good* booby feed. When we have travelled with ours over long distances as babies, they tend to go for a bit longer between feeds anyway because being in the car seat they don't seem to burn off as much food kwim?