They are treating her in a similar way to how they treated Princes Diana a lot of the time & honestly, I think other members of the royal family are happy to let that happen because it is a very effective distraction from all of the vile things some of them get up to.
There was a guy over here who did a couple of interviews a few years back about abuse he had suffered as a child, he did one interview with The Express newspaper where his name & face was shown (https://www.express.co.uk/news/uk/453381/Female-MP-abused-boy-in-care) & then later did another with BBC Panorama (where his identity was "hidden"). Since those interviews were released to the public, video footage has emerged of him naming people that neither The Express or Panorama included in their reports, he also insinuates that a member of the royal family was involved in some of the abuse. There is also footage showing him being coached & coerced into lying & including details that would discredit his own claims. I've heard this has happened to other people too. So yes, they have know for years & it seems highly likely that they have been covering up for him for a long time.