your being reactive to the chicks response. If it doesn't go good then you start reacting try to see how you can get that response that the friendlier girls give.
If your just starting out then its best to eject, but if you've been at it hardcore for about a month or two, it would be best to stick in the set until they walk off.
Another reason this sometimes happens is because the dudes expect the chick to talk and all of that right off the bat.
Be proactive, lead the conversation use illusionary input to make it seem like she is giving something in the conversation. Talk, Talk,Talk, Talk. My general rule is to keep talking for 10-30 mins (Calibrate) and just keep conveying your personality.
Ejecting from these sets and saying its boring sets is basically the guy trying to run away from a challenge and want to get only the easy sets. At the end of the day though its the guys lost because he will never be able to get women who act like that at the start. Once you get passed all of that the chick drops all of that and you get to actually have fun.
My general rule is that the set is boring because YOU made it boring. If a different guy was to go in there he could make it fun and then the previous guy is standing there wondering WTF that set was boring before but now it seems like the coolest chicks in the venue. It's because of the guy who went in, he brought that out of them eventually.
When I game personally the girl doesn't really have to say much because I will do things to get her talking. Later on in the interaction I'd kind of just sit there and build up the tension and make her feel the social pressure so she can sit there trying to think of something to say to restart the conversation. This is when it kind of goes about 50/50.