“Lovely family,” another wrote.
One commenter wrote: “Louise looks like a young Rosamund Pike!”
Rosamund Pike is a British actress who has played a Bond Girl and also Jane Bennett in the 2005 Pride and Prejudice adaptation.
Lady Louise will be competing in the events tomorrow.
Last year, age just 16, she came third in the event.
Sophie Countess of Wessex said of her daughter: “She is naturally so good at it, she really is. It’s something that she has taken to very well.”