"Anata" is often used between people who are a couple, so Nitori seems to be calling Hina "darling" in her thoughts.
I totally get you, Nitori.
Hina's... joyful facial expressions are pretty too, huh...Hina can make those kinds of expressions as well, huh...She's not my Hina (darling) alone anymore, is she...Now...That thought made me feel a bit lonely......Really, thank youYou're welcomeIt's all thanks to Nitori