Maybe line the car seat with a light blanket or cot sheet... Been caught out too many times by a nice chuck half way through the trip. Had one just the other night. Had to get Jesse out on the side of the road, just going on dark, strip him naked & try to redress him...trying to clean handfuls of vomit with wipes... not fun! Least then you could take off the blanket, change her & put her back in a clean seat. Make sure you have a spare plastic bag for dirty stuff