The event started on Thursday 15 May. It appears that Lady Louise is not taking part in the Carridge riding, nor is her mother, this year. Link below for Getty Images from Thursday (the Duke and Duchess of Edinburgh attended) and yesterday when they and the King attended.

https://www.gettyimages.co.uk/search/2/image?events=776320121&family=editorial&page=3&phrase=royal%20windsor%20horse%20show%202025&sort=best