I'm not sure how big your goals/dreams are, but I'll give you a quick reality check as far as competitive snowboarding goes. If you push yourself and work hard I think you would have no problem competing on a small-scale, but if you're having fantasies about going semi-pro don't get your hopes up. There are tons of kids out there who absolutely kill it doing freestyle who are as young as 8, so at your age and skill level it's just very hard to accomplish this. My biggest recomendation to people is to go snowboarding to have fun, and if improving your freestyles skills is fun, go for it. If it's not - who cares. There are lot's of us on this forum who are great freeriders and just aren't interested in park; and vice-versa.
If you do want to push yourself, I'd suggest trying to find a buddy or buddies to ride with who are better then you. Not only do you get to observe what their doing, but the peer-pressure really helps to make you push yourself and commit to stuff you might be scared of. The park scene is always intimidating from the outside, but I think if you go out and just ask if you can watch or ride with people - or even just ask for some advice it will break some of the ice and make the situation more comfortable. You have a big advantage being a girl too - guys are much more willing to help out a damsel in distress then some other random dude.
With learning anything new in snowboarding, the biggest thing you can do is to mentally commit yourself. Last minute bailing is what almost always ends in physical injury and injury to your confidence. If you amp yourself up and just go through with it - no matter previous experience, you always pleasantly surprise yourself.
PowderHound and TreeNinja