Same as "It's I" - aktiv form, so it's not "her" but "she
"It's I" sounds strange. "It's me who did it." - much more better.
more usual, but AFAIK wrong - but language is a living being, wrong becomes right, and I know that only a minority says "it's I"
it is her,who did it
How are there 71 people who think that it's 'her' who did it? Are 40% of these people illiterate?