But but, she stood up! That clearly proves she's the real one despite only Slaine's crew and Inaho's crew knowing there is two princesses and hime has been fake for the last two years.I can only imagine how baffling it must be for the average Terran in-universe. Asseylum first came to Earth for peace talks, then post-assassination still wanted peace talks, then she wanted war, then she marries Slaine and wants to create a new nation, and now she marries someone else and wants peace again.
In all seriousness, they probably think she was being used by Slaine or something. He is Terran born scum after all.