There's no way of knowing when Abby's mother or dog became seriously ill-- so probably it makes no sense to assume it was any particular time. As for menopause, I can't imagine that that explains anything here. Whether Abby's change, or deepening of her skepticism and dislike of Kelly in particular, but also Christie, is attributable to just the passage of time and repeated provocations from them, or whether it can be explained by Abby's just become too caught up in a role, or inability to deal with grief is just so speculative.
I do think she's been pushed to the limit by Kathy and Kelly in particular-- I mean how often is it okay for people to hit her with their pocketbooks, or their hands or other implements, pull her hair and twist her head or just plain old scream at her with the sharp piercing lungs of a Kelly? I personal think Kelly has been provocative since day 1-- in fact, I've never seen anyone who was so eager to see any turn of events as a huge grievance as Kelly is. But at what point does Abby have the right to say, enough. Maybe she's overly competitive, too focused on winning over everything, overly partial to Maddie (certainly openly) or overly impressed by her own persona-- but why is everyone and their cousin allowed to hit her? And what does it mean to say she deserved it? Maybe it seems trivial to you, but I wouldn't like to be a punching bag.
As far as Abby's pointing her finger in Kelly's face-- as it progressed, Kelly had begun to stick her finger in Abby's face, which was why Abby (rather childishly) started biting at it. If it's so awful and provocative for Abby to do it, would it have been equally okay for Abby to have hit Kelly and grabbed her hair and pulled her head around the way Kelly did with Abby?
Being dislikeable doesn't really make it open season on someone.