It is sad to see people quite the game, but I think this has been the weakest yet. It wasn't due to a nagging injury or a huge blowup with someone, she quit just from general Survivor stuff, which everyone else manages to endure.
I'm not saying living in those conditions is easy, but as you said, they have water and food, they just had a big feast, and she had it relatively easy around camp. As far as Survivor goes, she had it just fine.
I think it says a lot about how cushy her life is outside the game that she couldn't take it. Not that I'd even do as well as her, but I'd have the sense not to sign up for Survivor and take the spot of someone with a chance.