It was only after being with Mark and Arit for more than three months that Luna realized that Arit wasn't just acting the way she was acting to keep up appearances. Arit genuinely saw Luna as a friend! Luna watched Arit for a while longer, and she noticed that the main reason for Arit's closeness to her was that Arit just didn't have any other female friends in her life.
There was no one else around Arit that she could talk to about things that only women of her age would want to talk about. Arit didn't have a mother, sister or anything else. The closest thing Arit had to a female friend was Jeanne, but Jeanne was more of a mentor than a friend and Arit never felt comfortable joking with Jeanne because of how much she respected her. And with how possessive of Mark Arit was, Arit wasn't comfortable becoming friends with anyone else because she was worried that they might try to seduce Mark, and she would have to kill them.