The translation "Who is she planning" does not make much sense to me. The sentence needs further explanation, such as "Who is she planning to invite?" or "Who is she planning to exclude?". I have been caught twice on this!
Twice now I have been caught out using 'it' for elle and il. How do I know this isn't 'Which plan is it'? This sounds much better than the first option given here. ' She plans who?' that is complete nonsense in English.