If it does, it would seem to me that she is attacking a key witness who could help her go after the perp. Why would she do that?
I didn't take it to mean that she was attacking a witness. I thought of this scenario:
LS ODs and someone knows she has, but doesn't call 911. Instead, he leaves her, then returns, or takes her somewhere (like 5N) and then later, disposes of her body. I felt like CS's statement was to say, "Listen people, if you walk upon something like this situation, you don't just walk on by. You call 911. You stop and help for God's sake."
Or, another scenario could be that there was something seen on the vid in the alley. We've all questioned how her wristlet/keys were discovered so soon after LS went through that alley, yet no one claimed to have seen/heard them. Perhaps CS knows that someone surely did see and/or hear something and just kept walking. Perhaps she wasn't really "attacking" a witness, given this scenario, but maybe she feels that he's had far more than enough time to come forward and now she's just sending out a "WHO does that?!" message.