This boils down to which kingdom gets to pick who they fight in a 3 fish fight. I have always advised my kingdoms and Absalom kingdoms that if a kingdom wants to fight you (and that kingdom is a worthy match) that you should not try and run from the fight by instead choosing a more suitable target quickly to avoid them. My kingdoms have never done that and we've instead stood and fought the kingdom wanting to fight us even when outmatched and even when it resulted in a month of mutual destruction. I've always advised other Absalom kingdoms to also play this way although at times not all have listened.
The first thing we all need to recognize is that this "1v1" stuff is indeed an artificial construct largely put in place by top kingdoms and alliances with Absalom being the most obvious early proponent of. The game lets multiple kingdoms fight one kingdom just fine. Looking at this aspect, it would be very foolish to wave another kingdom when another strong kingdom is in the process of fighting you and has made it clear that they intend to full wave you and have already sent you a dragon and hit your cow. To quickly instead hit another kingdom is really to try and abuse the artificial "rule" of not hitting into "hostiles".
I've always also been a proponent of using common sense and not abusing some set of artificial "rules" to take advantage of situations such as by dodging a fight by quickly waving a kingdom that you feel to be an easier match. Likewise it would be an abuse to have 4 kingdoms all do 7 hits on one and claim no hostile so it's fine just because none was given ingame.
Use common sense, don't abuse rules (especially artificial ones), and don't run from fights by quickly initiating easier ones and everyone will have less trouble. This statement goes for everyone abs or not.