Long-story short. I met this girl in my UNI class 3 weeks ago; I went to talk to her after class and told her I found her pretty and that we should get together for coffee. I took her number, texted her and we met briefly for an hour. Then I texted her to set-up another get-together, to which she replied that she would let me know if she had too much work to do that day. On the day I wanted to see her she never ended up confirming on anything, no news at all. I didn't recontact her at all and it's been 2 weeks of that. I see her in my classes but we never speak.

Anyway, I've moved on, this post is not about her, it's about the term "ignoring". I have a couple of questions for the experienced dudes out there who have probably seen this a bunch of times and can share some insight.

When a girl ignores you or "flakes", what are appropriate signs to signal whether she just isn't interested or that she's playing hard to get (or in some cases that she's intimidated?). Usually I can tell when a girl just isn't down and I move on quicker than wildfire but for this one some of my friends seem to think I should have rekindled something. One of my friends who does some pick up says that a lot of girls he bangs will flake once and freeze him out until he contacts them again.

Now from the male's perspective, when do you guys find it appropriate to "ignore" a girl instead of moving on? If ever?

So, bullet points!
-Signs she's ignoring you because she's not interested and signs she's ignoring you for other reasons
-Recontacting girls who flake
-Using indifference versus simply forgetting about a chick?

Thanks