•Well to start, Kakashi might have it in his mind to force away the feelings for this girl once he understands she’s in love with Itachi. Even if she doesn’t outright admit to it (though that’s probably the case if we’re going off of the original team 7 thing right?), Kakashi will probably be able to tell, because he’s intuitive and can read people. So he’d know he was setting himself up for disaster from the start

•But assuming he couldn’t help himself and still loved her, he’d just sit with the feelings, never planning to confess. At least not in the beginning. At first Kakashi just deals with it. Pretends it doesn’t bother him when she goes on about how much she loves Itachi. Forces himself to seem interested and involved, especially when she asks stuff like “So…. what was Itachi like back when you were in the Anbu together?” And also, Kakashi doesn’t ever try to disparage Itachi out of spite. He knows that would be petty and would probably upset her, which is the last thing Kakashi wants to do. At most, he might avoid talking about Itachi and change the subject when possible

•Kakashi is fair though. Mature and logical. Kakashi knows Itachi has his problems… and also, this is all depending on what time we’re talking about with Itachi, pre-massacre or post-massacre. But regardless, Kakashi knows Itachi holds a certain appeal. Even if this is a random AU where the massacre didn’t happen at all, then yeah, Itachi’s a pretty cool, respectable, prominent shinobi. So Kakashi understands why she’d love him, and puts down any envious and jealous feelings he might have

•If it’s post-massacre, and she’s still in love with Itachi while he’s been designated as a rogue ninja, Kakashi will comfort her through the inevitable turmoil, even if he realizes there are lots of moral principles she’s probably breaking by remaining in love with someone who murdered his clan (at least until Kakashi learns the truth behind what really happened)

•And Kakashi will probably never tell her the truth about the massacre either. He’d respect Itachi’s wishes to keep it secret, even though he at times wants to tell her so she doesn’t live with this whole “I was in love with a murderer” type of ordeal

•It’s going to hurt Kakashi to comfort her as she longs for another man, but he’ll do it regardless because he wants to help her and can’t stand seeing her so despondent

•As for confessing, unlike the Naru/Sasu/Saku problem, Kakashi would probably never make his feelings known or obvious to anyone. He figures that would make everything messier, and he wouldn’t want her to feel sorry for him or anything like that. It would just be insulting

•But as mentioned before, he probably wouldn’t do anything in the beginning. Which means there might be room for a confession at some point. After so many years, Kakashi might just hit a point where he’s like screw it. But he’d want to make sure turmoil with Itachi had died down. Maybe it’s a long time after the war and the shinobi world has settled down. No more Akatsuki and obviously, no more Itachi. Kakashi doesn’t really see that as an opportunity to slide in and be her man or anything, like he doesn’t take advantage of that. But he knows it puts her through the stages of grief until finally, and hopefully, she comes to settle with it

•Okay but anyway yeah, he might confess to her later on. Even if he still loves her, he hits a point where he knows it’s been going on for so long that he shouldn’t expect anything to come out of it, so he doesn’t have much to lose. He’d just come out and tell her one day, but making certain to stress that she doesn’t have to feel bad, and definitely doesn’t have any obligation to him, even though he was at her side all those years and stood as her pillar of comfort. Basically, he doesn’t expect anything in return

•Conversely, it’s highly possible he could have already lost feelings for her after so long, and moved on. He’ll still know in his mind that he really loved her once, and he’ll retain fondness for her, but he doesn’t hold onto it because he knows it’ll prolong his grief