I dunno. If she was really that inaffectionate to KAITO, she wouldn't have let him inside in the first place. Remember, in popular belief, Rin tolerates KAITO the most out of any of them (next to Miku in some cases).
Small details, Haku and Ruko switched sides while she was opening the door, and it looks like the door did as well. Ah hahaha~. I'm just being an ass, I really like this series.