I wholeheartedly agree with this post.
There is absolutely no way of knowing whether it would have made one single whit of difference had the R's or KK's friend contacted LE. We'll never know.
I'm sure the unanswerable, "What if I had called LE?" question will haunt both the R's and KK's friend for a long, long time. I actually feel quite badly for them. JMO.
The blame lies elsewhere and needs to be laid solely/wholly/entirely at the feet of the individual(s) who actively planned and executed the murder.
I do think that had KK reported the solicitation attempt(s) to LE and/or contacted KB to alert her to the danger that PF posed to her, KB would still be alive.
IMO, the only individuals who could have prevented KB's murder are PF and KK.