I'm sure the jury agrees that KK is a horrible person for not doing anything to stop the murder and not going to LE before she got caught.
I'm not sure how important it is if they don't believe she cleaned up the crime scene because she wanted Kelsey's parents to know what happened, or that she left evidence behind so investigators would find it, or that she was afraid of PF.
All those things involve her reasoning and her feelings and her fear of looking like a bad person.
What they are probably more concerned about are the details of the crime, the sequence of events, and the evidence that matches her story.
They want to know how the crime went down.
Naturally she feels guilty and is going to make excuses for why she didn't do this or that or why she didn't tell anybody. But those things are harder to prove, or disprove.
As long as she isn't lying about her involvement, or anything she knows about the actual crime, I would think they would find her testimony credible.
Imo