If a girl is not genuinely interested in you, but is leading you on for whatever reason, it will abruptly come to an end once it has served its purpose.
My first job right out of college I was working for the Texas legislature in Austin editing legislation. My department consisted of two types: "lifers" who were local musicians and who needed a steady paycheck. When the legislature wasn't in session, they could record music, or tour and play gigs. Then there were people like me, who were young kids fresh out of college and were temps just hired for the session.
There was this girl, I'll call her Amanda, that came on real strong to me, over the top flirting. I was too young and naive to see it for what it was. There were almost no negative signals. Her behavior was entirely consistent with high-interest. Of course, what she was really up to was that there was a "lifer" there, about 10 years older than me, that she really had her eye on. She was trying to get his attention and make him jealous. It worked. As soon as he started paying attention to her, she stopped paying attention to me. This whole process lasted a few weeks at most. From that I learned that until the girl is sliding up and down on your d*ck, you can't really make any assumptions about whether or not she is into you, or if you are just Plan B or Plan C while she hopes Plan A comes to fruition.
I had another girl that I carried a torch for far too long at the height of my AFC days (I still have my AFC tendencies that I'm working through now, it's very much a work in progress). It started off with some mutual flirting, but it never got off the ground, and she went off to grad school in another city and made it clear nothing was going to happen between us. A few years went by and we kept in sporadic contact through email. I had gotten to the point where I had accepted nothing was going to happen between us and I wasn't making much effort to return her emails that came in once or twice a month. This is of course when she started paying me lots of attention out of nowhere. I'd send her an email and instead of waiting two weeks to write me back, she was writing me back the same day. Soon we were chatting all day every day over g-chat. Then she invited me to come visit her where she was living on a weekend (4 hour drive away). So I went down and visited her, things seemed to go real well, and I left her place that Sunday thinking we were finally going to be dating. Uh, no. She pulled a 180 and made it clear that nothing romantic was ever going to happen past that weekend. I'm guessing she must have recently gotten dumped, or was hard up, horny and lonely or something. I didn't realize it, but I was Plan Z break glass in case of emergency.
When a girl is really digging you, it begins like Ben Johnson coming out of the starting blocks in Seoul. There is steady and consistent escalation until you're f*cking her. If there are stops and starts, and you find yourself wondering where you stand with her, it means she's not that into you or she's keeping you in the picture just enough in case her Plan A doesn't work out.
