The mother-of-the-bride shared her usual reminder post on Instagram, telling fans that at 4pm she would be reading a children's story alongside a guest on her YouTube channel.
WATCH: Everything you need to know about the secret royal wedding
Sarah wrote: "Today at 4pm on @storytimewithfergieandfriends I am going to be drawing Baby Elephants with @davidwilliampress and my guest friend is @mark.lisk #storytimewithfergieandfriends #childrensbooks #books #stories."
Fans couldn't help congratulate the Duchess on her joyous family news. "Congratulations to your daughter Princess Beatrice and Edo soo lovely to hear some good news for a change. I hope you all have a beautiful day #proudmum," one follower replied, while another posted: "Many congratulations on the wedding of Princess Beatrice and Edoardo. Wonderful news. You must be very pleased x."
"Congratulations to you all today! What a wonderful day I'm sure you're having xx," came a third response.
Sarah has been reading children's stories on YouTube
Sarah tends to pre-record her Storytime videos, so it's likely she will have been able to enjoy the day fully with her daughter and her new son-in-law Edoardo Mapelli Mozzi.
A palace statement confirmed on Friday: "The private wedding ceremony of Princess Beatrice and Mr Edoardo Mapelli Mozzi took place at 11am on Friday 17 July at The Royal Chapel of All Saints at Royal Lodge, Windsor. The small ceremony was attended by the Queen, the Duke of Edinburgh and close family. The wedding took place in accordance with all relevant government guidelines."
Sarah and Beatrice at Princess Eugenie's wedding in 2018
Like her younger sister, Princess Eugenie, Beatrice also married in Windsor but rather than hosting the ceremony at St George's Chapel, she chose the more private Royal Chapel of All Saints.
The Grade II-listed church is located close to the Princess' childhood home, Royal Lodge Windsor, where Prince Andrew, Sarah, Eugenie and Jack Brooksbank have all been isolating during the coronavirus lockdown.
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