Removing her would have delayed the flight, possibly coursing it to miss it's take off window and have to wait for the next gap. At best it would cause a headache for the airspace control people, and at worse piss of hundreds of passengers if they then have to wait on the plane until the runway is next free.I really don't think they would have done that lightly.
He may or may not of been an entitled arse, but he had specifically paid to be able to cut the line, so reasonably did so (if this should be available is another question but that's not the fault of the individual). She then seems to have started harassing the guy, for doing something he's allowed to do, making her the aggressor in this scenario. To be honest if someone was verbally abusing me all the way from security through the gates and on to the plane I would feel pretty uncomfortable too, and clearly the staff felt it was responsible to remove her or they wouldn't put themselves through all the extra work.
As an asside, if I was in anything other than slip ones I would automatically let the next person go ahead while I untied laces etc. Surly most people would.