This topic actually just came up for me a few days ago. I was reflecting with one of the girls I daygamed about how we met and she said that even though I was charming and she was attracted to me, she was a bit leery at first because she wasn't sure if she was just another girl I met, or if I was just at the mall to pick girls up. According to her, what really helped me out was acknowledging that this wasn't a "normal" experience for me and that I'd really just been compelled by her beauty to actually drop what I was doing to come talk to her (which I really was!). Girls like to feel like they're unique and special to the guys they're fucking. And since then, I've modified my approach to make it really seem more like this isn't something I do often. I must say, the results (as far as flakes) are paying off positively.
On that note, I wouldn't come across to her as "shy", per se. But I do think that you should make an effort to convince her that you were just caught off guard by how attractive she is and you had to go and talk to her. Come across as social and confident, but avoid looking like you're out with the specific intent to "pick up chicks."