Helian Nana, before she married King Rui, was a little princess of the Northern Barbarians. As the Crown Princess of the Duke of Qi of Dayue, Su Luo could refrain from paying full respect, merely exchanging polite greetings among peers was sufficient.
But now that she is married, she has become the official wife of Rui King.
As such, Su Luo's status would be one rank lower, and to pay full respects to her was appropriate.
Not only that, but Su Luo should also pay full respects to King Rui Wei Jin.
But firstly, apart from formal court occasions, generally in private, the various princes took a friendlier approach and often didn't let people pay them full respects. Secondly, Wei Jin has always harboured such feelings for Su Luo; he naturally indulges her quite a bit.