That doesn't sound like an ESTP at all. Most of us tend to be very blunt about what we're doing. My friends know exactly what I think of them, both the good and the bad -- which isn't always so easy to hear, but it means they can never doubt where they stand with me. It's a pretty ESTP thing to do.
Now, we can be pretty damn manipulative if we decide we don't like the person and want to screw with them, but it's not a competitive thing so much as it is our mean streak surfacing.
And to be honest, everything you've described of her is just sloppy, sloppy, sloppy. Maybe she's an exception to the rule, but ESTPs aren't usually that reckless. We're planners when it comes to doing such things so we usually come off as more polished than that.
Like I said though, that's jsut ingeneral. She could be a very immature, very bitchy and very selfish ESTP who needs to be stripped of her rank and flogged in town square for making the rest of us look bad.
Honestly though, her actions don't read as ESTP to me. It sounds more like she's trying to get a rise out of you to see how much she could get away with. That sounds more like a Fe type screwing around with you to create drama.