It makes sense that the Pied Piper could also have been her Elder - he was a bad guy in the fairytale, so he probably would have been on the dark side. He could have given her a flute, like his. She could have been up with him, and used her flute to lure him into Death Valley, like how the Pied Piper led the children away from Hamelin, and let the monsters get him.
My favorite Virginia Dare moment was when she comes back from shopping in San Francisco and Dee says that she looks lovely and she replies "I assure you, everything was very expensive and it was all paid using your card."
I also agree she will probably teach Josh air magic in Book 5.