Once you check in and check any bags, take your pup back outside to empty her bladder.

If you get to the airport and get checked in, then find out that your flight has been delayed for 3 hours, take her back through security and take her for a walk. You'll need to judge how long it should take you to get through the TSA lines on your way back inside, but that would give her a chance to relieve herself before the flight.

You may want to bring puppy pee pads with you, and line her carrier. You can then change them before boarding the plane. I'd suggest doing this in a bathroom, if possible one of the family bathrooms that have a locking door, if the airport has those.

If your dog can go an entire night without needing to go outside, why not talk to your vet about giving her some Benadryl or such so she sleeps for much of the trip?