I agree with Paco that all = all [of them / the people], but it also seems to me that D could be an answer just as well as C. There's nothing wrong with the past tense here:
I know that all were getting on well with her the last time I saw them.
I got a sentence from a book:"How are things going with you?" So we can say" Things are going well with me." Can we also say"All is going well with her"?