The 26-year-old wrote in her Closer column about the alleged leak of Aguilera's pictures and warned stars to be cautious about keeping their private lives private.
She said: 'Last week, Christina Aguilera reportedly left her camera memory card in a French hotel and now intimate pictures of her and her boyfriend Matt Rutler, are being touted around.
'I'd be mortified if that happened to me, you have to be careful about what's precious to you. There are things about me that nobody knows - I work hard to keep parts of my life private.'
Kelly also praised Britney Spears for how good she is looking at the moment.
She added: 'I watched Britney Spears on Good Morning America and she looked beautiful. Everyone slams her for being out of shape or not wearing make-up or cute outfits, but she can do what the hell she wants in her spare time.
'Let her wear sweatpants - she pulls it all together when it matters!'