Definitely ask her out on a date, take her somewhere when you can talk, the movie theater would be a horrible option because you can't really talk, so skip that for the first date.
Maybe you should invite her over to have lunch with you, take her somewhere not so expensive and where you both like, you have nothing to lose asking her out on a date, but don't ask her to be your girlfriend just like that, because it most likely won't work, you need to get to know each other, you say you haven't really talked to her much, so you probably don't know if you still like her or not, so a date for now would be the best option.
Also if she says no, don't feel bad and don't let her know that you're down because of that, just say "Alright maybe next time!" and just keep on walking with a smile on your face
You need to be confident at the time you ask her, otherwise you'll seem way too shy and she won't feel comfortable :/ Also let her know that you like her for something else, don't just stay a friend, you need to man up and tell her how you feel, anyway I hope this helped in any way and good luck
