Stiles and Isaacs relationship always made me so happy. I always got the feeling they were kind of fighting over Scott's attention and rights to be his wing man. And I always thought there was a little extra tension between the two because of Scott. And I think Isaac moving in with Scott definitely amped it up for Stiles a little bit. Of course it would have only been fair for Stiles to take to Derek the same way;)
Stiles is like her best friend, in fact. He's the person she contact first when something goes wrong and the one she wants to save first in this case. Maybe she loves him without admitting but it's sure he's the person she is closest in the show.