I think especially with girls, there needs to be a social, fun element. My son was inspired when he was asked to be included in a performance at camp, and as part of his "Rock Camp" last summer. There were a bunch of girls that got into it too. Those situations inspired him more than when he is home alone working on his scales. We also made music practice required to earn Wii and computer time. A good 30 min practice earns 40 min screen time.

I am trying to think of when young girls sit around and jam, and unless you have some sort of camp or band situation, it is hard to make it social. But I think having some social connection with friends helps.