When the girl displays only the tiniest bit of interest in you, yes, I'd definitely try to talk to her more often, and eventually date her. Maybe she's really cool, but just not 'girlfriend material'. In that case, you might have yourself a good friend.
She knows you dated the other girl, and it didn't work out. So what? Happens all the time. If you get to have a connection with her - you know, this feeling you guys really start to 'know' each other - then what does the past with the other girl matter? And really, there's only one way to 'connect' to this girl...
By the way, what I try to do now is not to ignore anyone anymore. For me, it's not only the dating 'skills' that count, but, more broadly, the social skills. I have a feeling they're closely related.
Oh, that goes for talking to guys, too. Some guys just totally ignore other guys, and they only go after the girls. Not smart, in my opinion, even when in a club setting. Social people really seem to be the most attractive.
