Angela Mollard from the New Idea Royals podcast claims:
"This is a very special friendship between this 61-year-old dresser and the 93-year-old monarch.
"To such an extent that people say she is almost like another sister to the Queen after she lost her real sister, Margaret.
"There’s been conversations about Angela recently because the Queen has apparently given permission to write a book about their friendship. Very little is known about it."
According to Express, the dressmaker is likely to open up about her unusual friendship with the Queen in a book after securing the monarch's consent.
"Angela Kelly did say, back in 2007, that ‘we are two typical women – we discuss clothes, makeup, jewellery. We say, would that piece of jewellery look nice with that outfit and things like that," said Mollard.
"She has gone on to say that, at times, her closeness to the Queen had caused jealousy among other members of staff. She once jokingly said, ‘I don’t have any more room for knives in my back.
"She also said, 'I don’t know why the Queen seems fond of me but, because I don’t give her an easy time'."
What's more, the British head of state is said to have a code amongst staff members to meet with her personal assistant for tea.
The friends are believed to have a "hilarious time together" while discussing their "grandchildren and great-grandchildren."
Mollard states:
"There’s a bit of a code in the palace that when the Queen is popping out, it’s often to go and have a chat with Angela and apparently they can be heard in a sitting room laughing their heads off over a cup of Darjeeling tea or at Angela’s grace-and-favour home at Windsor, which the monarch gifted to her.
"Apparently, they just have a hilarious time together, they talk about everything and anything from grandchildren and great-grandchildren to new brands of makeup.
"They are very close and the Queen regards her as an absolute touchstone not just on matters of fashion but on matters of life.
"She’s her window to the world.
"What’s interesting is that Angela is a Scouser, a working-class area of Britain and she’s in this very posh environment - her former husband said she’d always wanted to work for royalty and that her relationship with the Queen is very close and she’s very dedicated."
Angela Kelly's job titles include Her Majesty's Personal Adviser and Curator, The Queen's Jewellery, Insignias and Wardrobe, Senior Dresser and In-house Designer.
The Queen also appointed Angela - who has worked with the monarch for 25 years - to the Royal Victorian Order for her personal services.
In fact, Angela Kelly is the first staff member of the Royal Household to be provided with permission to write a book about her time with her majesty.
According to Express, Kelly is also known as the Queen's confidante and "gatekeeper."