Some off the cuff thoughts... You're being younger than her really surprised her, she wasn't expecting it based on your appearance (dress/looks/mannerisms). She was clearly interested, maybe now she's worried she's going to look like she's being a bit predatory. I think you should get in the driving seat and get the ball rolling: "Hey, I loved chatting with you. I know a great <whatever> round here, let's go this Friday."
In other words, be the dominant alpha, act as if it's completely natural that you are leading the relationship, and so live up to your initial impression of being older than you at first seemed. Age isn't such an important thing for a guy - who you are is.
Just my 2c
P.