Relief
It took Blaise months to identify the feeling that Tir gave her, it wasn't love, she could recognize love. It wasn't lust, well there was that too, but she was used to that. No, this was different. This made her chest feel light and made her happiness, although that wasn't exactly right either.
He never looked at her with concern, the way Thierry did, he never scoffed at Blaise the way her Circle Midnight friends did. Tir didn't act as good as Thea did all the time, he didn't make me feel guilty the way she did when I wanted to cast mischievous magic. He accepted me when I was happy, no matter what I was doing, he had fun whether we were feeding pigeons or turning football players into parasites. For the first time since her parents died, Blaise felt like she could just be herself.
It took Blaise months to give name to the feeling he released in her, more than love or lust, more than happiness or contentedness. She realized that what he gave her was a break, a mini vacation, a second to relax. She realized she needed him for the relief he granted to her as her soul seemed to be tearing itself apart inside her chest.