Is it bad to be young and on datings sites?

I had a girl introduce us at our church June of 2011. She was young, and immature at the time, which I wasn't aware of. She threw me under the bus online, and left me high and dry for a guy who claimed to know me that fall. She really did a number on me. I've been stable for a few months now, and I've moved back home with my folks temporarily. I've gotten a few accounts with some dating sites for young adults and college students both. Unfortunately I have to see the ex girlfriend every Sunday at church which is an obstacle in itself, but I've been blowing her off. I haven't ever had much luck with the dating sites, so I'm not sure if it's embarrassing or not. I've seen several girls I'd love to date but I go genuinely care for the ex girlfriend. She's young and defensive and shallow, but I'm working on focusing on myself. I'm just wondering how I should perceive this?