How can i get an older girl to like me?

so i like this older girl she is 25 and im 21 we have know each other for bout 10 yrs since i was 10 and i feel like if i do a move on her it might be very weird because we have know each other for so long....there are time when she look at me and smiles... lately when we go out with a group of friends it looks like we have a good time but i feel like i might be taking it the wrong way i have no clue what to do. i want to get with her but i feel like we are completly different and she might not like me