I think Ash just simply doesn't fancy her. Maybe at first he was attracted to her, but her prickly personality and the atmosphere and the aggro she causes probably put him off. I mean, what man would want to get involved with a nasty, spoiled woman and be walking around on eggshells all the time. She's a nightmare and any sane man would avoid her like the plaque relationship - wise. Well, I would anyway!
I think he just likes her as a mate, but by the wary look on his face tonight when she was going off about Christopher I think he's getting fed up with her.