
Back in the 1990's, the last thing that the Spice Girls would have done would have been that of being impolite towards media representatives and especially towards the paparazzi that were following them all over the place. Because doing something like that would have led to fewer albums and other related items, ergo, less money for them.
Ever since the Spice Girls split, the girls' careers went downhill, with a few minor exceptions. Sure, some of them still sang and performed (Mel C, Emma), while others desperately tried to prove that they
can sing (Victoria, Mel B). All in all, their professional lives, after the group fell apart, were well under the level of their Spice days.
And, because she no longer needs the press, Mel C no longer has to play nice and smile and pose. So she does what every other human being does when annoyed like hell, and gives the finger. It's something most parents insist a lot on their children not to do, being a proof that they were not taught otherwise.
But Mel C no longer cares and, being a big girl and all, decides to go against her mother's teachings and just does it. There it is, for everyone to see. And, guess what? When she did that to the photographers that were (after all) only trying to snap a quick picture of her and be gone, we were also included...