Originally Posted by jxbrenna:
“why doesnt donna turn into the master like everyone else in the end of time? was it stated why as i cant recall it being.”
As vrooom says, it's because Donna isn't completely human any more. The event that created the copy of the Tenth Doctor is described as a 'biological meta-crisis', specifically a two-way one - just as the copy received some human DNA from Donna (one heart, for example), Donna received some Time Lord genetic material too, expanding her mental capacity.
Yes, it's all very silly and not really how biology works at all, but in the context of the story, Donna was far enough away from 'human' that the medical machine didn't match her template.