I am watching my friend's dog and it has gone crazy, what do I do?

Lock the dog in a bedroom. Is the dog ok around other people? Maybe keep your dog in part of the house and the other dog in another part of the house. I believe that she would be sued, but you could be too, because you were taking care of the dog at the time. The dog won't be put down. Usually there are three reported bites before a dog gets put down.