In my game, Castilian Mexico (my independent colonial state) is currently fighting British Mexico (Great Britain's colonial state). It's a war started by the other side; but Britain and me are at peace, which means I can share provinces with the troops of British Mexico without fighting.
I don't want to start a war with Britain at this point. Is there any other way to support Castilian Mexico other than declaring war on Britain - money, ...? (Or to influence Isla Juana, another one of my colonial independent states comprising almost the entire Caribbean and their next-door neighbor which currently just stands by idly, to make them help their Castilian Mexican brethren)
Any ideas appreciated!