It's perhaps not surprising that Rollins would fall for a character like Murphy. The SVU detective is burdened with a litany of unresolved issues from her abusive and atypical upbringing, and in some ways, Murphy represents the protective and empathetic father figure Rollins never had. At the same time, Murphy is mostly absent from Rollins' life — much like the father she actually had — which allows her to keep him at arm's length in an endeavor to protect herself from disappointment. Her relationship with ADA Carisi, on the other hand, represents some serious emotional growth for the character, who was previously unwilling to make herself vulnerable. Unlike Murphy, Carisi has always been there for Rollins and her daughters — both emotionally and literally — and it finally looks as though the troubled detective might be moving toward some semblance of stability.
It's no wonder that Murphy's return in Season 23 has some fans nervous. As user AmazeeDayzee noted on the series' subreddit, "I would like Declan to connect with his daughter but I don't want him and Amanda together or Amanda and Sonny (Carisi) to break up."
If anything, Declan Murphy's return (as the Captain of the Hate Crimes Division) suggests less that he might drive a wedge between Rollins and Carisi, and more that his desire to be involved in Jesse's (Charlotte Cabell) life might re-fan the flames of conflict between Carisi and Murphy first set-off by their interaction in Season 16. The actor behind Carisi, Peter Scanavino, has been tantalizingly vague on the subject. As he told TVLine regarding Murphy's return, "I don't see how it would be anything contentious or dramatic, but who knows? It's the name of the game with this show. So, it could be. I don't know."