The writers and producers have shown normal friendships or friendly interactions among team Flash members in all seasons, which indicates that showing those friendships is a priority for them. Those strong bonds are what makes team Flash, "a family". This has been a priority since S1.
Here's the thing: Caitlin/KF tried to kill Cisco and Barry, too, but that didn't dampen their friendships at all. If this was the real world, their friendships would have ended once she tried to kill them. The writers and producers wanted to keep them bonded and they expanded these bonds beyond Barry, Cisco, and Cait in several ways. Let's just discuss Iris and Cait's expanding bonds.
With regard to Cait expanding her bonds, she reached out to Joe in 4x1, offered an apology for what she did to Cecile, and hugged Joe. Have we seen Caitlin hug Iris? I don't recall. Caitlin never reached to Iris or apologized for what she did to Iris on Savitar's behalf. Caitlin took initiative to have a Jitters get together with just Joe in S4. Caitlin has asked Joe for his advice. The only time I recall Caitlin asking something of Iris was about info. on the burning man in S1. In fact, Iris was the initator in most of her "friendship" interactions with Cait in S4, which was very one-sided.
Joe didn't make an excuse for Caitlin when she apologized nor did he coddle her when he outed her manipulating the team to work with Amunet. The closest Iris has come to putting Cait on blast was for a split moment in 4x1.
Even Cecile and Caitlin have a sorta normal friendly relationship based on Cecile telling her about Thomas in S4, and they shared that side-eyed grin when Nora insulted Iris at the baseball game in S5. And when Nora blocked Iris' calls, she didn't block Cait's number in S5. Caitlin and Ralph have done the buddy storyline about breaking into Tannhauser Labs and went to the artic together.
With regard to expanding Iris' bonds on the team, since S2, we've seen Iris interact well with Cisco. In S4, we saw Iris interact well with Harry Wells and later, Marlize Devoe. In fact, I think Iris had more friendship chemistry with Marlize in two episodes than Iris had with Cait in 5 seasons. In S5, we've seen Iris interact so well with Ralph. And of course, Iris interacts well with Cecile; she encouraged the relationship with her father and talked about her personal fears and issues with Cecile.
The only wierdness in all the STAR Labs relationships is between Iris and Caitlin. The only reasons they did any psuedo-friendship between Iris and Cait in S4 was to:
Use Iris to absolve Caitlin without requiring Caitlin to apologize to Iris.
Get Caitlin into the WestAllen wedding party.
Deal with media scrutinity about the lack of friendship between the two women.
This isn't about writers not being into a Caitlin/Iris friendship. I firmly believe the writers would have written a normal, healthy friendship with an onscreen apology from Cait to Iris (like Cait gave to Joe) if not for some BTS shenanigans (strong dislike) between these two actresses. I suspect, too, that because AJK was in charge through S4.5, he wouldn't allow Cait to apologize to Iris as a favor to DP. These are the only things, IMO, that explain why these two characters have not been consistently friendly on screen since S2. AJK made sure the writing was one-sided; he made sure Iris, Caitlin's victim, did all the initiating, did all the coddling, and made all the effort to embrace the woman who tried to help murder her without Caitlin ever having to utter one syllable of an apology or be redeemed.
In S5, the two characters barely speak, rarely make eye contact, and hardly interact in any meaingful way. Think back to "Cause and XS"; Iris saw Cicada's dagger moving to kill Killer Frost and Iris didn't even look back or yell to warn her. Like not even to save her life would Iris make eye contact with her.🤣
If a novice watched the show in S5, they'd assume these two were enemies or very new aquaintances, not two people working on a team for 4+ years. With AJK gone, CP probably asked Todd to minimize their interaction; the S5 distancing is the result.