I would agree with most here - absolutely contact her. I have a stepdaughter who's 17, and girls that age definitely need all the positive interaction/role models they can get! You must have played a role in her life that was meaningful.
However, I wouldn't read too much into it until you contact her. I have contacted people from my past not because I needed/wanted something from them, but just because it was fun to hear what happened to them. Kids especially tend to have hundreds of "friends" on facebook, so she might just want to say hi.
Either way, you have nothing to lose by asking. And contacting her doesn't mean you contact the ex. Those relationships can be and should be 2 different relationships at her age.