How would you show strife in Amber reflected in Rebma?
Is it a direct correlation? If an Elder Amberite is killed, does a high ranking noble in Rebma die? If Random dies, does Moire? Do areas of the castle destroyed by explosions cause corresponding sections of the palace in Rebma to blow up?
Is it a reflection by mood? If there is something going on in Amber, are the people more likely to be irritable, or scared, or happy?
Is it a case of Rebmanians trying to follow the Amberites? If there are cabals going on in Amber, do nobles in Rebma start trying to be like them? Is it conscious or unconscious on the part of the Rebmanians? (Or should it be Rebmaniacs? Rebmans? Rebmen?)
Does the reflection go both ways? Eric didn't want to piss off Rebma too badly. What could Rebma really do to Amber? Make their oceanfront resort real estate unpleasant?
I don't think the relationship as depicted in the books is highly dubious. A parallel kingdom, with troops, it's own pattern and a powerful royal family just down the cliff? Unlikely.
In my Amber Rebma has been thoroughly annexed. A Warden of the royal family is given total dominion over Rebma.