So what i understand from reading Viella side story.

The planet actually have a will and is "Mother", she wanted Viella to remove all the living beings on the planet while she went to sleep but Viella misunderstood that the planet also wanted to die
The undertaker is actually the original Eva and not M.Eva who is her clone / fake
The ending of Monad Eva was Undertaker talking to M.Eva and not (you)
From what Eliza said Undertaker could be one of the original automaton
Undertaker seems to be angry at M.Eva because she forgot something which is either their real goal or real master who is probably not K