When the fans realized that Iggy wasn't stopping for an impromptu meet-and-greet, they started booing her as she made her way into the venue.
Iggy took it for a little bit and then once she was safely inside and surrounded by security, she flipped them the bird. Ouch!
In Iggy's defense, there would have been an even bigger group of disappointed fans if she was late for the show and she did tweet that she was sick, so she probably either didn't feel up to it, or didn't want to pass along her germs.
That's not to say we wouldn't have been bummed if we were waiting out in the cold to see her and ended up getting the cold shoulder, but we're sure she had a reason.