The actor, who is set to play Queen Elizabeth II in the third series of The Crown, was asked if her new role has given her a greater understanding of the pressures faced by the royals.
"It's just evil," she told The Mirror. "They're mean to them. Everything they do, they step outside their house and it's something.
"I don't know why they're so mean to a fellow human being. It always strikes me as odd."
The royal couple recently confirmed they will spend Christmas with Markle’s mother Doria Ragland in the US rather than staying with the Queen, a decision which has been met with some criticism.
Colman said: "Everyone wants a little Christmas on their own every now and again. It's alright."
The new episodes of The Crown begin in 1964 and will cover the Queen’s Silver Jubilee, the moon landing and Prince Charles’s relationship with a young Camilla Shand.
The Crown season three will arrive on Netflix on 17 November.