Not even trying to act cool but this hasn't happened to me in a while. Not even because I'm so good looking or so smooth. More because in the last few years I've only been giving my attention to girls who want me bad.
To answer the OP, she is doing this to test you. When you called and she didn't pick up, she knew it was you. She wanted to see if you would try again to classify you as thirsty (cause she's dumb). When you texted to say it was you, she felt like she had the power (again, dumb/immature). So she ignores you. Then you stop giving her attention, she realizes she might have misjudged you and starts sweating you again. They do it because it's in their nature to test how much they can control you. How much they can make you eat out of their hand. How far are you willing to go to get a chance at her. What is the best way to control you (sex, emotions, jealousy, ego, guilt, damsel in distress, becoming your momma and you being dependent on them to take care of you, etc, etc). They just want to figure out how to get what they want. They all do it. Some are aware of it. Some aren't. Some do it intricately, some do it in a tacky way.