After a while of tinkering I figured out how to work the command:
CompanionAddRelationship Companion_Aloth(Clone) Player_Watcher positive major 1
Switch out 'Watcher' for your watcher's name and spam the command a few times to raise the level of relationship. As far as I can tell +2 is the highest you can have it at, the other half of the circle would be filled with red if you were disliking each other and woud fill to a maximum of -2
Hope this helps!