Yep, I heard that Wills confided in Harry about a fake affair with Rose knowing he'd tell Migraine... because they suspected that Migraine was leaking family
tit to her mates (and thus the press). It started as stuff about the Cambridge kids, their nicknames habits diet etc and Kate got fed up with it so they set H&M up with the false affair story to see where it went and bingo. When Harry found out they'd been bluffed to catch Migraine out he was furious at them and that was a big part of the falling out.
There is no way in hell Kate and William are still jointly socialising closely with someone he's supposedly shagging.
Before they married Migraine was also escorted from the private living quarters of other Royals in Kensington Palace when residents complained she was wandering around taking photos.She was also escorted away from poking around in a car at a polo match, again pre wedding. She's a nosy cow.