I don't think it "clearly" shows any such thing. She certainly has the pot in her hands over her head, but whether she threw it at him or not is not at all clear from that video. It was such a short amount of time from when she grabbed it to when she was shot, she may not have even had time to attempt to throw it, if that was her intent.
Beyond that, the officer is not all that close to her at the time of the shooting; it looks like he's probably a good 5 or 6 feet from her. His attempt to justify the shooting by saying "And look, it came all the way to our feet, too" (in reference to the water) is laughable.
Frankly, he seemed to have escalated the situation unnecessarily. I don't think her use of the phrase "I rebuke you in the name of Jesus" can be considered a credible threat or reason for him to pull his gun and threaten to shoot her in the face. Unless there is video we have somehow not seen which makes it truly clear that the woman had thrown boiling water at the officer before he fired, it's understandable why a jury voted to convict.