I think it should be fine. I always had to drive long hours like that when I had my daughter. And if its a familiy gathering that should be fine to. I have a huge family in a small community and everyone was at the house when I came home from the hospital.
Ditto. Babies can be moved from place to place in a car, but what is waiting for them at the other end can be very hazardous to their health. If it is a family gathering, everyone will want to hold the baby, and stick their face into the baby's face, and at this time of year you can guarantee that someone in the group will at least have a cold. If you are mixing her formula, that is a lot of gear to take and it will be tough to be sure everything stays sanitary. I fully appreciate the desire to show the family the baby (if it is a family gathereing) but there is always Christmas.
It's not the actual traveling that might be a problem, it's where you're going. Are you taking her to a large family gathering where there will be lots of people touching her?
She's young to be out in public and exposed to all kinds of germs.