You'll get a lot of different replies! Are you travelling her and then going to a show? If so, you can't use anything with valerian in it. If not, then Wendal Herbs Special Calmer is good I have found. Otherwise Science Supplements ProKalm is really good, you can buy a trial size and see if it works before splashing out on a big tub.
a great big spliff stuffed with scag works a treat (if your anti smoke you could stuff a haynet) or....................'Bachs Flower Rescue Remedy'. Works a treat and is completely legal