Did I just get rejected? What does it mean when a girl does this?

I'm on online dating and I met a girl and she is a couple of years older than me. We never met face to face yet. Lately we have been text messaging every evening. When I text her she usually responds back within a couple of moments. Last night I didn't get back to her last text message because I fell asleep. Anyway she was the first to text me today. Which is always a good sign. She doesn't know what I looked like, so I sent her a picture of me. All she said was "gee you look young! lol" After that she didn't text me back. She usually texts me back. Is this just her way on saying I'm not interested anymore? Should I text again tomorrow? Wait a couple days? Or should I just let her text me? I'm not sure if she is interested and I'm not sure if this is some kind of game. Advice please.