It wasn’t deliberate, therefore it was a mistake. Caused by the negligence of the organisers and the presence of cameras IMO. She was angling her sign so the camera could see better, and neither she nor the rider noticed how close together they were
I think you fail to understand the difference between stupidity and gross negligence. She wasn't there to watch the race: her back was to them as she played for the cameras. You even fail to acknowledge the damage it causes to the teams and sponsors.
It is physically impossible to police the hundreds of miles that the peloton goes through, it has always required some self policing of the spectators, unfortunetly this is one incident that has broke the camels back, does she deserve the full backlash she has got, probably not, has she got the same response as some in previous years yes, does she deserve to be scapegoated because of her sex and try and pin the blame onto the organisers, no, the only people doing the latter are people who do not understand the sport.