Since the duke asked if Riina would normally be able to enter the palace, and she wasn't, then maybe he'll make it so that the gang can stay together since he knows they are all loyal to each other and get along very well. I think he'll make the proper adjustments for them. So I don't think her nor Jade will have to worry about being separated.
But I can't tell if Jade has feelings for Teresse, or if he just thinks of her as a cute little sister. I wonder if they were hinting that he took a liking to her romantically, so thats why he made up his mind (settling his romantic feelings) to just congratulate them wholeheartedly. Personally, I ship them, but Teresse only sees him as a big brother. But since they get along so well, they really would make a good pair.