She may have been on private property but the photographer was on a public road which makes a big difference. If she's silly enough to strip off in view of a public road (albeit some distance from the road) then she can hardly complain afterwards if people have seen her topless. She, or one of her advisers, should have been aware of this.
I think she/they are being rather naive about this. She's obviously in the spotlight, she was surely aware of this when she married a prince. Whether the magazine should have printed the photos is a different matter but , even if they didn't, they would still have ended up on the web for all to see.
Unfortunately, she's brought it on herself. Silly girl. She needs to think before she acts rather than the other way round.