I think it is mostly this authority thing - Nyn very much had the idea that if she married Lan he would be her wader ... so she would always be in charge, as she likes to be.

But the sea folks - have a rule that who is higher status in public has to submit in private so that means when they are alone, Lan is the boss I guess it is been really good for her to just be able to let go and have a man take care of her even if she didn't want it that way.

Somewhere it also said that she really enjoyed sex with him and the other girls thought she was making it up - but I'm sure it is quite true :-)