What should i do?

I went to high school with this girl for 3 years and now i have graduated and i am in college. She is a senior in high school and is 17. I'm 18. I never really got to know her and rarely talked to her. I saw her last week and now shes all i can think about. I never asked her out in high school for 2 main reason

1) She was my teachers daughter

2) My friends said i could do better.(looking back about that one i should of done it, with or without their support)

I've been thinking about going back to my high school and asking her out. I know shes single because i asked one of my old teachers that was her favorite teacher. What should i do?

and no i dont care that shes under the legal age because thats not what im looking for.

I know this is a repost but i wanted to add more info to it