Cops are there to enforce the law, not administer retaliatory punishment. Male or female, the accused should have been restrained properly and charged with assaulting a police officer. Since the cop took the law into his own hands and assaulted her in retaliation/punishment for her action, should she still be punished/charged for the assault? After she hit him, they should have put her down, handcuffed her, and book her for assaulting a police officer.
If the cop knocking her out is his way to stop her from her behavior, he sucks as a police officer. They failed at restraining her properly. Period. In the end, disproportionate use of force is, at the very least, clear in this situation.