Following the strict, technical definition of assault, yes, reaching for the drink was assault. Grabbing the drink was technically battery. Subsequently throwing the drink at her may or may not also be considered assault and battery, depending on how "provocation" and/or "instigation" come into play. Let's say it is. Let's say that the thrown drink was battery. He's guilty, he's an asshole, but his guilt was in responding to her attack. His actions did not justify her previous actions, nor her subsequent actions.
If you unjustifiably initiate a physical altercation, you are not justified in using force until you have first attempted to retreat from the altercation, or have been stopped, and excessive force is continuing to be used against you. She instigated the altercation: grabbing the drink. He responded, throwing the drink. She was not stopped, and had made no attempt to retreat. She continued the altercation by lunging over the table and striking him multiple times. He was justified at this point in shoving her away from him, which he did. She fell to the ground. Then she got back up on her feet.
The "questionable" conclusion depends on whether it was reasonable to believe she was rising to continue the attack. If she's the defendant on trial, then she is entitled to the evidence being viewed in her favor. If she's on trial, the kick was an unjustified continuation of his initially-justified force, and her subsequent actions can be viewed from that perspective.
If he's the one on trial, he is entitled to the evidence being viewed in his favor. If he's on trial, the kick was to put her back on the ground, stopping her from continuing to strike him.
Which part of that did I mischaracterize?