I’m confident that it does, since the portraits of the ambassadors from Mermaid Tale 2 were seen in Barbie: The Pearl Princess.
Now I’ve started thinking about how Seagundia and Oceana interact... if their portraits are hanging up in the castle of Seagundia, surely at least one of the ambassadors is from there... is Oceana a world power for aquatic kingdoms because its queen is the one that makes Merillia? Could Merliah and Lumina be related somehow?