While I'm at it, listening to your story kind of reminds me of a page from my life...
Almost 3 years ago, I met the woman I'm still with to this day, and I was also friends with my ex-girlfriend. Before I met my woman, though, I had tried to patch shit up with my ex, but she insisted that we stay "Just Friends." So I agreed to it, never asking her if she was seeing anyone, never calling her on a Saturday asking her if she'd like to go out, my treat anymore. I was just "a friend" from that point on.
She'd talk to me about her ex (the guy she got with right after me), but I wouldn't talk to her about who I was dating, let alone that I was dating anyone. Then, I met and started dating my woman -excuse me, My Woman, with a Capital W.

Anyway, little under/over a month into us talking, we started having sex, and my ex and I were talking less and less. She'd call me and jokingly say shit like "How are things with you and your new
*girrrrlfriend*?" I'd always laugh it off and change the subject.
One night, I hadn't called her (ex) back, because I didn't get in the house until about 4am, and had to be at school in 3 hours. Next day, I pick up my girl and bring her back to my house, where we watch some movie I had, and afterward had sex. Almost 5 minutes after I came, ex calls. She's on some old "I'm offended that you didn't return my call last night" type of shit. I'm laying buck ass naked on the couch next to my woman (although we hadn't made it "official" yet, that was our second time having sex), so I ask her if I can call her back in an hour. "Why can't we talk now? What, are you trying to woo your
*girrrrlfriend*?"
I say "Something like that, yeah."
*Silence for about 3 seconds*
Ex:Well, is it your girlfriend or not?
Me:Something like that, yeah...
Ex:Look, it's either a yes or no answer, is that your girlfriend or not?
Me:

SOMETHING LIKE THAT,
YEAH.
Ex:So you're trying to push me off the phone with you for some other girl? Is that what it is?
Me:

Huh?
Ex:Friends don't push friends away just for some random old girl they're fucking with.
Me:

What book did you get that out of? Look, lemme call you back, we can sort this out later, I got company.
Woman:Baby, you want some water?
Ex:Hmmph. Well look, you don't have to call me back AT ALL, EVER AGAIN, You aren't a real friend if you're going to choose--
Me: Whoa, whoa, hold on one motherfucking minute. When
WE were a couple, I asked you if it would be okay if I hung out with YOU and YOUR friends since you would always hang out with them on the weekends, only to find out YOU were CHEATING
ON ME WITH one of said friends, and YOU weren't even woman enough to come out and tell me that you didn't want to be with me anymore, I had to play detective. So you can take that hypocritical shit back.
Ex:That was different, I would've hung out with you and them, but you were being to close--
Me:WHICH IS WHAT A MAN IS SUPPOSED TO DO. Matter of fact, I don't know why I was so sympathetic to even try to rebuild some shit with your sneaky, two-timing ass. Don't call you ever again? You can bet on it. You'll be calling me before I EVER pick up a phone trying to get in touch with you.
*Click*
My Woman came out of the kitchen with a glass of water, a bag of weed and a life lesson:
"Baby, calm down, here, lemme massage your back. Calm down. Don't let anyone get you that upset.
If she was a real friend she would've accepted you and the fact that you've moved on,
and she would've been happy to see you happy. Life's too short to spend it sulking over a couple of missed calls. And, if she wanted you back, she should've been woman enough to say something before you found me."
Don't even sweat the situation, just accept the fact that she wasn't ready for what you had to offer, and that she fell victim to the 80/20 rule.