Oh god, the friend trap. Allrighty then ::cracks nuckles::
Actually, knowing her since 4th grade is helping you NOT hurting you IF you know how to leverage it.
The trick here is to totally challenge her
picture of who you are!
And, it stretches your comfort zone, which is good for growth.
Win-win
Ask yourself, neutrally, how you present yourself around her: Intellectual, reserved, rebellious, deep, friendly? Once you get that down, invite her on a date that is an activity that the opposite kind of person would do.
For example...if you're normally kind of intellectual, invite her on something that is more animal/athletic (I'm a fan of doing some three-wheeler off roading, followed by clubbing in that kind of situation).
Of course, use common sense, and don't invite her on something you know she'll hate...
What this does is create contrast. If you don't express interest, this creates mystery and excitement.
At that point, you're sitting pretty.