As long as the girl isn't being creepy about taking picture, you shouldn't even suspect a thing. Think about it: With social media, I can easily just scope you out on Facebook/Twitter/Google/online forums to get an idea: Most typically yield a photo, and then I could just tell someone, "Yeah, this is the kid I'm going on the date with." And you wouldn't even have known that you were already scoped out.
When I met my fiance five years ago, it was with a group of friends and at my track meet. The next few times we met, I was still with someone and my dad made sure to meet him early on (dad's a scary old man, 6th Dan and isn't afraid to tear people apart if it means protecting his family).