Usually you want to show that you are interested in someone soon after you meet them. If you do not escalate, the girl will move on. I personally have never been able to woo a girl 6 months after I met her. It normally is just a bad way to go about doing it.
If you want to try dating her now, then go for it. Here are some tips. DON'T tell her how you feel and force this issue. Don't sit her down and confess that you like her.
You need to try flirting with her a bit. Try touching her appropriately. Make good eye contact. Try setting up a casual meeting with her. I would try to ask her out 2 or 3 times. Try to make it sound like you just want to hang out with her. Then when you meet her act like it is a date. Calling it a date beforehand, might put a bit of pressure on her.
If she does not hang out with you and you tried asking 3 times, then move on. You're better off finding someone that is interested in hanging out with you.