Belle you are spot on. What is a constant with Mary is not just her seeking of the camera; but that her focus is upon it
and not on either what she is meant to be doing or who she is meant to be paying attention to (whether it be supervising her kids meeting and speaking with others or listening to speeches etc)
Moreover she compounds this horrid trait frequently by pushing in front of others; reaching across directly in front of their faces to wave and carry on; shoves others aside (as she has done with Derf) or simply remains rooted to the spot on the red carpet posing when everyone else has already moved on.
The shoving; pushing and reaching across peoples' faces I find particularly crass and ill bred. I tell my kids off for that kind of behaviour!