A Republic spokesperson warned "there is a strong feeling, even among monarchists, that we shouldn't be paying for Eugenie's big day ... the monarchy is stretching its public support to a breaking point".
Though she has a job, Eugenie is not considered a "working" member of the royal family meaning she is not obliged to carry out official royal duties like her cousins Princes William and Harry.
Robbie Williams' daughter Teddy has also been confirmed as a bridesmaid!
The couple, who initially met after being introduced by friends while Eugenie was still at Newcastle University in Verbier, Switzerland, will walk down the aisle at St George's Chapel, the very spot where the Duke and Duchess of Sussex tied the knot in May.
There will be only two page boys: the Cambridge's son Prince George, 5, and Louis de Givenchy, 6, the son of Zoe and Olivier De Givenchy. Since then the princess has posted a series of photos including some pretty adorable throwbacks of her and sister Princess Beatrice.
It has already been announced that 1,200 members of the public have been invited into the grounds of Windsor Castle for the wedding.
The Queen's youngest grandchildren, 14-year-old Lady Louise Mountbatten-Windsor and 10-year-old Viscount Severn will be Special attendants.
Jack proposed to Eugenie, whose mum is Sarah, the Duchess of York, with a padparadscha sapphire ring surrounded by diamonds.