She cried afterwards.
In her temporary TARDIS bedroom, she sat on the bed and wept. Those people, men, women, children, all screaming and dying in a terrible inferno and there wasn't a thing she could do about it. Donna didn't know the Doctor very well, not yet, but the research she had done on him during their time apart was not wrong: his constant companion was death, a list of the deceased followed in his every footstep, another tragedy lingered in his every shadow.
And he carried on.
And she had to too. Because he needed her.