Good for Rachel! She's my favorite actress currently, and this just makes me love her more
To echo what some have said, she doesn't need a reason to not want to pose nude, and it doesn't make her a prude. Nudity can be sexy, but so can leaving something to the imagination. And just because a woman has done nudity in the past does not mean her body is now public property to be exposed and put on display whenever someone demands. Just because you kiss a guy, doesn't mean you're obligated to keep on kissing him. Just because you've had sex with someone in the past doesn't mean they have the right to have it again if you don't want to. Nudity and the choice to be nude, whether in front of one person or an audience of many, is a personal, private choice that should never be expected or demanded. Years ago, in Hollywood, she would have shown up and been told to have sex with the man in charge or there'd be no shoot. Katherine Hepburn was labeled a "prude" for stalking out and refusing because that was the way things were done, and what's wrong with sex? I'm grateful for Hepburn's stand (and Jean Arthur's, who was openly, harshly mocked by the industry for her "prudishness") and I'm grateful for Rachel's. Would the hot male actor of the moment have had "you're going to be photographed nude" sprung on him with the expectance of compliance?
I think the unexpectedness of it was a big factor too. There a difference between knowing before hand what's going to happen, how you'll be shot, who will be there, what the photographer's vision is, etc, and showing up thinking you'll be clothed the whole time and being told to strip like you're some ho in an ameteur p*rn flick. It has to be degrading and embarrassing. She may have done the nudity if they'd talked to her before hand, she may have refused. But her publicist seemingly took away her choice in the matter and I am so proud of her that she realized she still did have one.