Noone is saying she is a role model, in the same way as Jessica Ennius or any of the other athletes on that stage. But I am struggling to see how she is the 'antithesis' of a role model.
She is a courteous, apparently pleasant young woman who has been in the royal family for a relatively short period of time and has started to do exactly what is expected of someone in that role, ie support charities and appear at national events. She is not being held out as something to aspire to - her role is a fairly unique one since the are very few heirs to the throne floating around out there for young women to aspire to marry - she's just doing what the royal family have been doing for decades now.
She's not taking drugs, falling out of clubs drunk, committing fraud, kicking puppies or shouting abuse at elderly ladies - she's just performing the role that goes hand in hand with the place she married into. And she's been at it for a fairly short time - who knows what she might do once she grows into the role and becomes more confident?
All she did was turn up at an awards ceremony, by invitation, and hand over a trophy. She's not making a political statement or trying to influence anyone. There were plenty of fantastic role models on that stage - it was about them, not about who presented the awards.
She'll never win. If she gets a job, people will say it's a sinecure and she's taking a job away from someone who needs it. If she works in a soup kitchen, people will say she is patronising the homeless people there. If she doesn't work, people will say she's a lazy, useless cow.
Just let her get on with what's expected of her without the bitching. When she does something wrong, or offensive, fine, criticise away, but I can't see that she deserves any of it yet.