It's probably an intentional thought. But the whole Kiara losing her memories permanently before seems to have been something Calli added herself during a Q&A as Kiara did not seem really prepared for that when it was brought up (and not in an in-character way).

I'm also semi-convinced that Calli herself didn't fully grasp how heavy that actually is. God. She's lost her once 'permanently' before and now she keeps a friendship with this Kiara because she just can't let her go completely. Being a native of the underworld she's always seen death as just going from our world to hers, but losing your memories is worse than death in this sense because that means the person those memories formed is forever gone. A real death but with no afterlife.

Imagine how freakin' jarring that must have been if they were in love? Death being a no-big-deal thing because it means something different to her. Then bam. One day she learns about mortal perspective of death when her love is just... gone. And now she's holding onto this her-but-not-her reincarnation that keeps trying to get with her, but may 'die' again, and keeping her at a distance is hurting her sometimes. Heavy stuff.

And though maybe unintentional I kinda like the dynamic where Kiara doesn't take death seriously, even kinda brushing aside the idea of permanent memory loss, because for her kind death is not a big deal. She just doesn't understand death. Meanwhile she's implied to be the immature side of the relationship, and misses all Calli's dere moments. As if she doesn't understand Calli, who as a Grim Reaper is Death.