First of all, you need to forget about the future meetings with her, regardless of she accepts or deny go out with you. This is normal, she is beautiful, lot of guys hit on her all the time, asking her out will show that you are confident.
Is not normal a woman to shout "hello" to someone that she unless don't have some consideration.
Say something like "You seems a nice person to me. Maybe we should hang out some time". Wait for her response, if it is positive or silence like a "maybe", continue with "give me your number and when I can call to you".
Hope it can help you get a date!
