Growing romantic interest for a friend I've had for a good chunk of my life

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I (M22) have a friend (F22) I've been friends with for close to 10 years now. We get along very well, and have told eachother things and information that we wouldn't trust others with. Until this year, I didn't have any romantic feelings for her since I was never ready to even give relationships a thought. We started going out to do things together earlier this year and as the year has went on, I couldn't help but start thinking about a future with her. We are both very shy, she more-so than I and because of that I have always been the one to initiate a plan. However, recently she asked if I would be interested in going to the movies with her, to which I immediately agreed to. Having said romantic interest in her, I decided to ask and see if she'd like to go for dinner or an ice cream parlor afterwards and to my surprise she just about immediately said yes to it. I really want to ask her if she'd be interested in a relationship, but at the same time I don't want to ruin what we already have and it's been consuming me because of it. How should I go about the situation at hand?