His reaction timing was incredibly fast, less than a second had it taken for Alec to realize she was pulling away from the kiss when he’d grabbed her and kept the kiss going. It scared her slightly, but she knew that was the least of her worries. She had walked into his house with a sick feeling in her gut, mixed with overwhelming fear for something - but what, she couldn’t tell. As she had assessed his condition within the moments following her entering his room, she had come to a disturbing conclusion. The boy she loved had been changed.
She felt it the second she had walked into the room, it had hit her hard enough that her senses hadn’t been sharp enough to pick up his tight grip on the chair until she was almost right at his side. When she’d finally seen it and calculated the risks to moving any closer she assessed that looking into his eyes might set him off. She knew she couldn’t do anything about his sense of smell, but his eyes would be the key. If he didn’t get to see her, then it might work out.
Of course, her judgment had been swayed as the love for him swelled in her and took over her rational judgment. The price could have been greater than she was willing to give. But somehow, Alec had fought through and given his love another chance at life.
It was only when she had fallen into his lap and then let him kiss her back had things been put to the test fully. It was only then that she had realized what she was dealing with. When she had looked into his changed eyes, she no longer saw the gleam in them, just a hunger - primal and sexual. Yet this hunger went far beyond the normal horniness she typically saw.
It had scared her, but more than that, she had also decided to put her love to the test then. Put his love to the test. She trusted he loved her, she trusted he could pull through just long enough to take what he absolutely needed, then find the rest as soon as possible. She knew she had to put the theory to the test, risking herself in the process. But if it worked, then it would be worth it. If she didn’t do this, she’d be risking his sanity, his will power, his life even.