She CAN sing, but as that proves she can only sing WELL when she isn't dancing/moving around a lot.

exactly john. people will say that anyone can't sing judging by live performances, but to be honest, when it's recorded in the studio they're not doing an elaborate acrobatic routine or having to belt it out massive arena style so it's hardly gonna sound amazing when you're making it harder for yourself. i don't even think it's the kinda song where she needed to move, so why they did it for the x factor i don't know.