Does she crave your attention more than Eric, does she want you knee and your time more?
I've found that things can go pear shaped with Bronte and Penny at times because they are both wanting my knee. If Penny gets on she growls at the others. If Bronte gets on she definately targets Penny because she knows Penny wants what she wants and Phoebe and Logan arn't really knee dogs.
I have to watch in certain situations that things don't get out of hand so when I know there is potential for a conflict, even if its just an air snap I can't let either of the girls on my knee.
Same with food, mine on the whole don't bother guarding food, it's gone too quick for that, but if I do have things that take longer to eat Bronte is always moved to a safe area because she'll try to pinch off the others. Logan, Pheobe and Penny seem to respect each others space and a little growl will move them on, Bronte on the other hand can't see why she can't have someone elses if she's finished, so to protect her she's put out the way. She'll also defend what she has if she thinks one of the others is too close.