She should sleep a lot of the time so mostly when you stop for you she will need to go too. You could just stop like say every three hours weather you need to or not so you can allow her to go first and put her back then you can go. Do what works for you. Do not be alarmed if she does not eat full meals on a road trip sometimes they don't.Give her water every time you stop or at least present it to her. My dogs are usually very good on a road trip. When we took Esa up to NY to have her bred back in March it was 6 hours up and back. We had to take Vinny with us, Esa would be staying there but Vinny traveled back with us. Esa is never comfortable in a vehicle but Vinny laid on his bed(always use a crate for the safety of the dog but Vinny rode up on his bed,he hates crates,which is not a good excuse) and slept the whole way up except for gas stops etc. Esa just shifts in her crate,but sat the entire time going up ,would not relax and lay down once. Have a good trip.