Its hard to give advice without having witnessed the events. There are always signs we may miss in the heat of the incident that we remember once we cool down. Is she sure the dog just went after her little dog out of the blue or did the little dog bring it upon itself? I feel it was wise to pick up her obviously outmatched dog, but foolish to turn away from the aggressing dog. Turning sideways to a threatening dog can calm the situation, but often times turning fully away willl incite a bite, as will squaring off with the aggressor. If she never saw this dog before, then it was foolish to allow her and other little dogs to remain unleashed in an area with a new and "unknown" much larger dog and new "unknown" owner. What kind of 90lb mutt would also be helpful to know. I've physically stopped attacks on smaller dogs or old and hurt dogs, but I'm also quite a bit larger than most people and most dogs are fearful of me at first. I know women who are much better around dogs to be able to do the same by being more knowledgable than I. I also don't let my dogs to dog parks, and don't let the little ones out without atleast 1 big one because we have stray dogs and coyotes always running through the neighborhood. The best thing she can do is keep socializing her dog, not coddling it and making it "face its fears" while she faces her own. Seeing your dog get injured can be traumatic and can be hard to come back from, but the only way to get over it is to keep living your life and going out of your way to get over it. Maybe not dog parking it, but "play date" and training classes would be smart.