What should I do or say to her?

I'm 16 and a Junior in High School. There is this girl in my French class who really stands out to me. She is not only beautiful, smart, and hilarious but every time she walks into the room my heart races and my stomach fills with butterflies. She says hello to me in the hallway and since we sit next to each other we are constantly talking. Today she needed help with her assignment (even though she knew every answer) she asked me to move closer to her and when I made a joke she would laugh and smile. We looked into each others eyes when we talked.... My other friend Kayla who was a lesbian said she has dated girls in the past, I know she dated a guy for a year who cheated on her and really hurt her.. What should I do? How are little ways I can flirt? Please help me I would really appreciate it! -Aly