How do I become more than friends with one of my best friend that's a girl?

So I've know this girl since kindergarten and she's my best girl friends. So now that were going into 8th grade, she matured A LOT and got so much hotter. We go to different middle schools, but we talk a lot and hang out. And when we hang out, we are really close to eachother and I give her piggy back rides a lot :D. Recently she found out that I liked her. I didn't mention asking her out cause I got really embarrased. All my guy friends are pressuring for me to ask her out because she doesn't stay single for long, but I'm way too shy to ask her out. What should I do?How do I become more than friends with one of my best friend that's a girl?
Ask her out.....Say, we are sooo good friends that we should go out. Then see how she responds... With a smile.... great !!!

Something else ,,,,, then sorry buddy. Then, you put a big smile on you face and say, JUST KIDDING. You can keep on being friends. Then try again next month.