Tearing her hair in frustration, Princess Bride KATE MIDDLETON’s in a tizzy because Grumpy Granny – aka THE QUEEN – just delivered a not-so-discreet decree about how to style her tresses when she weds!

Bearing the bad tidings, henpecked PRINCE WILLIAM was pained to inform his fiancee that Her Royal Highness told him during a visit: “Of course, Kate would never dream of wearing her hair down during the ceremony.”

Reports My Noble Spy: “Kate simply couldn’t believe what she was hearing. She told William: ‘You are joking, right? You can’t possibly be serious. She’s telling me how I must wear my hair at my own wedding?’”

In what’s become a pattern for man-in-the-middle Wills, he calmed Kate and begged her not to rock the boat.

“Kate finally shrugged it off – but told William she’s making no promises,” said the source. “His family will just have to wait and see how she decides to wear her own hair at her own wedding.”

Rolling her eyes, Kate – who’s actually not the rebellious type – started experimenting with different hair up-do’s.

“She doesn’t want to start the marriage off on the wrong foot, but she’s growing more sympathetic to PRINCESS DIANA. She told me, ‘I’m finally realizing what William’s poor mum must have gone through with this family.’ ”