From my own personal experience with this type of scenario, I would not call this girl, or even email her back. The ball's in HER court now. In other words, she's the one who needs to be left in the cold. Sure, she just supposedly got out of a rough relationship ...or a relationship with a guy that had a rough ending. However, she's got no right to just go around and try and be this way with you or anyone else. She's (from this brief story) sounding like she's trying to jerk you around and be manipulative. I've learned to never let a girl manipulate me and get me to do what she wants. You just met this chick. It's not your job to be there every time she calls. Even if you guys were full on dating, and you knew more about her, you need to set boundaries. You dont need to express what these boundaries are to a girl verbally. You set them by the way you act. If you meet a girl somewhere like in this situation, you dont call her right back. If you call her right back when she expects or asks you to, youre setting yourself up to be in control by her. When I meet a new girl, I call her when I'm ready to. Usually a day or so after getting her number. A girl needs to know her place so to speak. I'm not going to be mr pussy whipped and predictable.
Dont call her or contact her again, give her the "cold shoulder". If she wants to talk to you badly enough, she will go out of her way to do so. You need to act like the man here. Whether youre the shy type or not does not matter. It seems like from the scenario you have shared here, that you are not exactly hard up. Sounds like you have plenty of access to environments, and groups of friends that can help you meet women. Just like men, women enjoy the challenge of "the hunt". Dont be mr easy to get to. If you never hear from this girl again, so be it. "NEXT!".
Dont let girls mess with your head either just because you wont play their little game. If they say youre being an "asshole" because you dont have your cell phone shoved up your ass and youre not waiting with abaited breath for their every call, the hell with them. Lots of fish in the sea man. If this girl calls you back, you might say something like you just like to get to know a girl before moving any further, or you felt like she was trying to rush things faster than you were ready for. Whatever you say (only if SHE calls) dont act like the little guy with no balls. I've learned that even though they do have the pussy, they dont rule the world. If youre a decent looking guy with a good personality, you wont have problems meeting women. You just need to make sure you dont let women control how things move along.
Also if it sounds like she's hooking up with someone else, and you know the sources are reliable (people telling you so) I probably would not talk to her again even if she did contact you. If I did happen to talk to her again, I'd let her know I was not the type that hooked up with easy girls...of course not letting her know that I knew she was laying it out for someone else. That can be another way of trying to manipulate you as well because women know that people talk. Sometimes a girl will makeout with or even fuck someone a guy knows because they know that someone will tell the guy theyre trying to get to. They do this to create jealousy, and to see if they can get to the guy emotionally. Girls like that are not worth my or anyone else's time. They're sluts, and sluts deserve what they get. Which is usually either a gutter, or another asshole boyfriend.