She's much like me in this: she's a total outsider, completely unsocialized. Raised in a really unhealthy foster home til she was 12, then lived on the run for six-seven years doing... unfortunate things in order to survive... not only is she learning about Shayara and the ways of her people, but she's learning about people in general. And she's fairly resistant.
And it takes a talk with Ryan to make Kieran realize that she doesn't hate him as much as she wants to... because if she did, she would be avoiding him entirely. She's bitchy and belligerent to him, but she is talking to him instead of to Donna or Ryan, so she's obviously got some degree of interest. Not romantic, not sexual, but she's attempting to figure him out. She's just really hostile about it for her own reasons.