But the thing is, Stella is from Tenebrae... Niflheim is the country that invades. I really don't see at all how Romeo and Juliet are compared. Romeo and Juliet isn't even a love story to begin with, it's a three day relationship against an emo depressed guy who gets dumped and gets a boner with the first girl he saw basically.
And even though Stella isn't with the country that invaded, they already said higher-ups in her country pressure her into fighting with Noct over the crystal. Other countries want the crystal since it's the last one.