Most Helpful Girl
One thing girls-shy or not-tend to do, not all but most, is use jealousy. You said that you ignore her messing with your buddy, but that's clearly not what she wants. She wants you to acknowledge it, become mad, have some type of reaction. So yes, she may come off as thirsty, but usually you can tell if a girl is really into a guy or just being a flirt. If she really is playing hard to get, most chances are that she is into you and wants this to push you to make a move.