When Rollins and Carrisi are walking down the street at the start of the episode and they come to the corner, they see the "star" in distress. The camera angle then comes from behind the star and you do not see Carisi and Rollins in the scene at the corner.
Kelsey is being given preferential treatment because of being a woman, as they are intending to charge Austin with domestic assault but not her. It is sexist and a double standard for only the man to be charged, especially when the woman was the first to become violent. Their statements, and the evidence, show that she hit him first, with the champagne bottle, then he later hit her in the eye. If police had this situation in real life and one of them insisted on pressing charges they would both be charged. The only time in a situation like this where only one person in a domestic dispute gets charged is if they inflict far more injury than the other person. While that did not happen here (at the point before they are engaged) Kelsey is actually the one that caused the more serious injury, hitting someone with an object is always a more serious charge than being slapped.