The whole thing was a mess and the explanation of her comments (which by her own admission were expressed clumsily) was accepted. She wasn't attacking white people and she wasn't harassing the police officer on account of his race. Therefore she wasn't found guilty of the charge of racially aggravated assault.
She was saying that she felt her experience and the way she was being treated was typical of how brown people have often been treated by white police officers (the Met have admitted they're institutionally racist so it's not a wild idea.) People can argue over whether she was correct to draw that conclusion and how much of a role alcohol played, but the motivation and intention of her comments were accepted and it's pretty easy to see why if you read the transcripts.
Should she have been blind drunk in the back of a taxi? No (Although if she was a premier league footballer she'd have probably just driven herself home in that state and all would have been forgiven). But everything that happened after she vomited out of the window of that cab was insane and inflamed the situation.
Personally I think it's entirely believable that they thought they were being abducted. And I think that is evidenced by the fact they called 999 from inside the cab whilst they were locked inside and being driven somewhere unfamiliar. The dispatcher said they'd call them back and hung up on them. Never in my life have a heard of a taxi a driver being asked to divert a passenger to a police station. It beggars belief. And also would not have happened if it was two blokes in the back of the car. If it were me, I would have gotten very paranoid about what was happening to me too.
When they got to the police station and told the police they had made a call for help they were told they were lying. That was incorrect and frustrated the situation even further. It was proven in court that they did in fact make that call.
Furthermore, she was arrested for smashing the back window of the cab even though her girlfriend had already admitted to it and confirmed she wasn't involved. This made her feel even more unheard and targeted.
Throw into the mix the officer using language like "little missy" and making light of her concerns about being raped and murdered and it's conceivable that she felt she was being treated badly. She filmed the whole exchange herself which a pretty strong indicator of what she was feeling at the time.
Do I think she behaved like a drunken dickhead that night? Yes. As do thousands of people every single weekend. Do I think I think the decisions taken by the police that night inflamed things? Absolutely. Was no need for it to ever end up in court.