That is incorrect. She did not have any head-start. Watch the picture below. Her bat is still inside the crease as the bowler entered her delivery stride.
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Now let’s compare it to Ashwin’s Mankad against Sri Lanka in 2012. You can clearly see the batsmen leaving the crease as Ashwin entered the delivery stride.
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If a batsmen leaves the crease as the bowler is entering the delivery stride you should definitely run him out. However, if you are deliberately stopping before you release the ball even though the batsmen was inside the crease when you entered your delivery stride then it is an underhand tactic and should be strongly discouraged.
I am a strong advocate for Mankading but I cannot condone this. Very poor behavior. Judging by the timing of her movement, she is basically leaving the crease at the point where the bowler was supposed to release the ball. That is fine and most batsmen do that. However, leaving the crease while the bowler is running into ball and entering his delivery stride is obviously unacceptable.