I keep toys nearby to distract as soon as stuff like this happens, or
covered bowls of crunchies that I can whip out and give them a treat. If
said behavior happens again, I put agressor in time out for a while. It
seems to have helped a lot between Pearl and Grant or even Pearl chasing
Sugar. I can even sometimes just put Pearl in the bedroom (time out) without
closing the door and she will get up in the cat napper and  and chill on her
own. Time out seems to work really well. It's not much "punishment" with a
big window, cat tree, cat napper, bed, food and a litter box, but it is
"away". So, I don't feel bad about it and whether its Grant stalking Pearl
(though usually it is Pearl stalking Grant). After a break of about 20
minutes to a half hour, they will then studiously ignore each other for the
most part.  Main thing is to BE CONSISTENT with both cats.

Karen