She described the Duke and Duchess of Sussex's big day as a "beautiful wedding" and wished them all the best for the future.
For the occasion, Joss wore a sleeveless floral dress, a pair of black Hobbs shoes and a Hobbs cluster bag. Then she put all the items up for sale on ebay, there were 48 bids, and when the sale closed on Sunday, the winning bid was £511.54.
Joss is donating all of the money to the charity Sentebale, of which she is an Ambassador.
Founded by Prince Harry and Prince Seeiso, the charity helps children and young people affected by HIV in southern Africa get the support they need to lead healthy and productive lives.
It's not the first time Joss has helped people in Africa. Last year she visited two refugee camps in Djibouti and the Joss Stone Foundation was able to gather more than 250 instruments to give to them.
Joss has so far visited more than 150 countries on her world tour which started more than three years ago. She has performed in towns and cities from Egypt to South Korea, and Monaco to Toronto.
She had been in Qatar prior to the Royal Wedding, and then flew out to Baltimore and the Bahamas before moving on to Jamaica and Antigua.
Next month she will be in Italy, Germany, Czech Republic, Portugal and Chile.
Joss was born at the former Buckland Hospital in Dover and went to St Mary's Primary School before her family moved to Devon. She has made several return visits to her home town, and delighted fans with a concert at the town hall in 2009.
