present one (our German Shepherd #9 if I counted correctly), named very aptly Pasha:
, if your dog tends to get travel sick, mix a bit of ginger into her food. It works miracles.
Also, some flight companies allow well-trained dogs in the cabin. If yours doesn't, you could add to her comfort in the freight compartment by giving her an old shirt or blanket of yours. The scent might comfort her when she gets scared. In the worst case you could ask your vet for a mild sedative.
Also, maybe the flight personnel allows you to check on the dog during the flight if you ask nicely.