I agree it wasn't Tesla-hate, but notice the SUV directly in front of her, which is a wider vehicle, is also directly centered in its lane. And, the rider didn't slap the SUV's mirror.
Your presumption that this biker is a Tesla "hater" is about as valid as our postulation that your sister as a biker "hater".
Given that she lives in Cali, where lane splitting by motorcycles is legal and is to be expected by all drivers, the obvious needs to be stated - she was hogging the right-dividing lane and blocking the motorcycle! He sent her a message not to do so again, without any damage done to the car.
With some luck, she learned that lesson.
If she didn't, you need to explain it to her!
Whether you like lane splitting by motorcycles or not (personally, I am not a fan), you need to be aware of the rules of the road in Cali, and leave bikers room to pass.
Similar to right-turn-on-red - in some states it's legal, in others it is not.
Adjust your riving behavior accordingly!