so for example if Su Yang had accepted, Princess Bao Yang would’ve had a hold on her and would be able to pressure her into doing something she doesn’t want to.
so possibly one of the reasons Su Yang risked offending a royal by refusing her gift is she didn’t want to be beholden to that person, especially since so many people witnessed it. something like, “no, we have no ties and i don’t owe her anything”. especially since we have already established she knows the princess likes the young general and wants to stay out of that potential mess.