I agree but itīs also the reason I think she was being controlled, he actions donīt make sense otherwise. The overmind gave her free will from himself but he is unable to create a being free from the "Voice in the Dark". He needed a being that controled the Zerg without BEING a Zerg. Kerrigan being deinfested was part of the Overminds plan but not part of the vision because Blizzard didnīt want to spoil the ending.
If she is controlled it makes sense that she would be forced to try to destroy the one thing that would break the control.