Hi, Kaworu:
First off, welcome to the group (I think). I’m so sorry you’re suffering.
Second off, I’m old enough to be your mom and I’ve been through what you’ve been through. I won’t give you “mom” advice because I don’t have children (and if they were like me they wouldn’t listen anyway)

Even though I am female I can be extremely unforgiving for things done by my sex. Women can be terribly cruel (but so can men).
To get to your concern:
1. You had this female friend that, for awhile was more than a friend and it appeared the feeling was mutual.
2. You wanted to “pop the question”. What exactly do you mean? Not *the* question—at least I hope not. I think you’re waaaay too young to even think about marriage. Or are you talking about “do you want to have a mutually exclusive relationship (we used to call it “going steady”)”?
3. She found someone new and has pretty much put you out of her life, but then she’ll ask questions that people ask each other (“how ya doin’”, “long time no see” and the like). You may not realize it but people ask those kind of questions just to make superficial conversation (it happens in the working world). It’s not like they necessarily care how you’re feeling unless that person and you really are friends.
4. You’re heart-broken because she’s dropped you. I’m not certain what you mean “denied everything”—what did she deny? Is it possible that you put her on the spot with some kind of an accusatory question and it was easier her to cut the conversation short and just say something to drive you away?
Do I have this right?
So why do women behave that way? Because right now she’s fickle and immature.

I must admit that I did that when I was in the first year of secondary school (or do you call it “high school”—from some of your terms you’re either from Canada or some place where British English is spoken) I was “in love” with a new guy every couple of weeks or so it seems and the old guy just ceased to exist because of the infatuation with the “new guy”.
I ignored the “old guy” because it was just easier than to tell him that I had a “new guy”. I know it hurt him a great deal but we both ended up getting over it and became close friends over the years. It was never a romantic thing, I would just go to his parents’ house, sometimes for Sunday dinner, more often than not to play “cut throat Monopoly”. In fact, we saw the very first episode of _Saturday Night Live_ at his place.
Anyway, I know you’re hurting about “her” but you have to accept the fact that she’s moved on. Not that you have to *like* it; acceptance has nothing to do with liking or hating a situation.
You do sound like a very nice guy, but I think it’s time you move on. Love can be an illness, but it can also be very nice. To sound cold and analytical, friends are like habits—you pick them up (the habit/the friendship) and it’s hard to break (when the relationship ends and you beat yourself up and are miserable). Break the habit of thinking about what happened (easier said than done). Find something new that interests you—I would think that there are plenty of things at university that you can get involved in. OK, you may have to be dragged to a couple of meetings but you may find that you end up enjoying them and in the process meet a group of people who share your interests.
Maybe “she’ll” come back to you as a friend. You know at least one of her major faults so you can decide how much of a friendship you want. If she does, take it very slowly because there’s always a chance that she’ll play you for a yo-yo (because you’re pining for her she knows that you’ll always be available until the next guy comes along). I’m not saying that the next “Significant Other” will worship you, she may treat you like the first one, but that’s the chance you have to take. After all, the chances of a relationship lasting are 50-50.
You’re going to have your heart broken a few more times and each time it will really hurt (even if you get married you’ll have your heart broken, trust me), but each time you’ll learn lessons.

Get your life together, buy that car and take care of the things that you need. Define yourself in terms of “you” and not in terms of anyone else because when you get down to it, when you feel everyone else has abandoned you you’ll have to rely on yourself.
Also, my dear, *you* didn’t lose a friend, *she* lost a friend. You may have been the best thing in her life and she was too stupid to realize it. Unless you’re not being entirely honest, I can’t see what you did to push her towards someone else. She consciously made the choice to find someone else; you didn’t make the choice for her.
I hope this helps a little. Please keep posting, and remember, it’s OK to cry. It’s quite normal to mourn the loss of something or someone. Time heals all wounds (and time wounds all heels).
Good luck.
P.S. I got married for my first time when I was 38 (I know, I was a fossil!) but that's because I did things I wanted to do for myself and figured I'd never got the chance once I got married, and I wanted to get myself as independent as possible so I could rely on myself when times get bad (and not that I'm strong when my heart is broken--I fall apart also).
Is this making any sense? I tend to ramble.