Claire couldn't let herself think like this. She was only being affected after seeing those other girls check Alex out as if he was one of them instead of getting the weird looks he had in the beginning when they were out in public.
She wasn't the kind of person that would let a random man live with her. He was only allowed to stay here in the first place because of extenuating circumstances.
When they first met he treated her as if she was a rather interesting species of insect. Cool to look at but could be crushed at any time. He always looked at her blankly with no emotion whatsoever.
He didn't know anything unrelated to his former profession either so once she got past her fear of him deciding she wasn't interesting anymore and killing her, she had trusted him. He did save her life multiple times in a few weeks, after all.