Zira did try to take Kiara's paw, after she swiped at her
she realised she was'nt going to climb back up herself and
tryed to climb back up when it dawned on her that Kiara was
actually trying to help her, like SimbasGuard said, she was
so consumed with hate that she could'nt see Kiara wanted to
help

Zira did try to take Kiara's paw, but only to try to kill
her. Zira only wanted revenge and not reason. Just like
Simba said to Kovu in before the part when he was ambushed.
Scar couldn't let go of his hate, and in the end it
destroyed him. Same goes for Zira. But I can't help but to
think that it might have been a hint that she was going to
die ya know.

Zira was so consumed with hate rid that She would rather die
than be helped by Her enemy.