"Hi X, it's nice to meet you!" "Oh we've met already!"

[gee_ess]

I agree. Leave the "It's nice to meet you" completely out of your conversation. Smile, act happy to see the girl, say something like "Hi! It's good to see you! How are you this morning?"

And I really like the suggestion above about not putting yourself down by saying things like, "I' am SO bad with names!"

Also, when thinking about my own situations where I run into someone that I think I already know but am not sure, I make sure the tone of my conversation sounds like I know them.

For example: A perfunctory nod of the head and straightfoward, "How are you?" is WAY different than a big smile and body language that says I recognize you, and then the genuinely warm, "How are you?!"