[Angus]

We're witnessing three different styles of bitching here:

Nicola, loads the gun and gets one of the others to pull the trigger - usually Denise - so that Nicola gets the result she wants without the blame. This is called third party, or intermediary, bitching.
Denise, pretends to be joking around when she makes her nasty, snidey comments, so she can accuse her victim of not having a "sense of humour". This is called deflection bitching, putting the blame on the victim.
Natalie, plays the non threatening girl next door type who starts every bitchy comment with "I'm not being horrible but......, or "I'm not being rude but......., in order to get her digs in but still retain her sheep fans' following. This is called apologetic bitching, allowing herself a get out clause if she notices adverse reactions.

Usually the house can cope, even thrive, with one uber bitch, but here we have a trilogy of saddoes who have each perfected their individual styles of bitching to the nth degree and whose uniquely jealous and egotistical personalities have drawn them to each other to form an unholy alliance to turn bitching into an olympic sport. Between them they are ruining the show.