I wouldn't ask her until you come BACK from wherever you're going. After that, invite her on a small, short date with just the two of you. Something like coffee or studying together or a walk in the park.

Believe it or not, girls can be scared of commitment just as much as guys. Dinner and a movie means she has to dress up, stress over how she looks, and spend a whole evening with you. Something shorter and lighter is more appealing.

If she accepts, you're already in good shape. Be sure to keep things light and positive. Bring your best smile. After your short date tell her that you had a lot of fun, and you want to do it more often in the future. She'll probably catch on right away, but if she doesn't, keep trying, making the dates a little bigger and a little more involved each time.