Once my friend had the same problem with hers. After a few months (she got some advice) her dog seems to be fine to her already. She told me if my dog appears to be like that it's because I'm not showing who's the leader here.. not sure if it's true since it hasn't happened to my dog.
Animals have it's own personality, you just have to find it.
Even if you hire a trainer, the training needs to be done by all members of the family. So if your friend is going to continue to allow the dog to do what it wants, then a trainer is a waste of money. Teaching the dog right from wrong is important to keep it out of trouble, and even injuring its self.
I would suggest a trainer asap, and your friend needs to be told she has to continue training after trainer leaves. Obediance class is wonderful, but the owner must continue the work even after class is over. A good dog is a trained dog, and it takes work and patience.