That might be worth doing if I had Stephen King's following. But what I had in mind was to use two full books to complete the story. In the first Marian would prevent DeFalco from doing something that would leave him and the NYPD open to a lawsuit. Instead of being grateful to Marian for saving his neck (a nice-person response), he would resent her all the more for showing him up. Since they no longer work out of the same precinct, he can't get at her that way. So he starts a campaign to discredit her with the higher-ups in the NYPD, laying behind-the-scenes traps for her. All of this would be only a secondary plot, running behind the main plot of the mystery (to keep the conflict from becoming just another in-house squabble). But the first book would end with Marian's understanding that DeFalco is no longer just a thorn in her side but a declared enemy and she'd better do something about it. The second book would show what she does.
Now, all that's a lot of work. And I'm not willing to invest two years of my life in the hope that e-publishing will suddenly become profitable for those of us who aren't Stephen King. And self-publishing is out of the question. As Tony Fennelly so acutely put it, "Paying to have your work published is like going to the prom with your kid brother."
I'd rather just let the whole thing go.