I've got some great news about Abbi and Ateret's involuntary project the past few months to modify their naughty behavior toward one another and get along: We've achieved success!
The girls took part in a special study earlier this year to see if a new product would change aggressive behavior in multiple-cat households. I thought we had the product and not the placebo because Abbi and Ateret's behavior improved. Then, about a week after the product that was delivered via two infusers faded away, the aggression began again.
Having enjoyed the fairly peaceful behavior of the month or so before, I decided to try putting pheromone collars on Abbi and Ateret to see if things would improve. To my great surprise, the collars, although somewhat smelly for the first few days, helped calm things down.
After two months (collars only last 30 days), I decided to take September off without special collars to see if they'd been reprogrammed, so to speak. Lo and behold, the naughty, aggressive behavior that has characterized the last four years (since Abbi moved in) is gone.
So, I highly recommend trying pheromone collars made especially for cats. If two pushy girls like Abbi and Ateret can benefit, your friends might be helped, too.