When your race grants you many advantages like aptitude for magic, long life, agility etc. You will look down to anyone (not only race) without them. I'm talking about the many representation of elves in RPGs - they usually portrayed as aloof.
Elven matriarch forces herself onto others like it's the most natural thing in the world. So it's true what's said about them not caring about consent.
Elven supremacist, matriarch (a potential femme fatale in the world of politics?), and head of a (dubious) religion. Damn, we got a triple-whopper of an evil character here, and I thought the emperor was bad.
Simple, just continue the statement of never having heard of that, with saying you will check with her if it is true and then send a message with her response to the invite + whether it is true that she is engaged to that guy. Then when she says no to both, then put that in the message.
That is...really stupid. Like "I'm tempted to drop the story" level stupid.
The writer expects us to believe that a foreign ruler can just claim that his daughter and her son are engaged and this king will have no choice but to roll with it because his daughter isn't there to deny it? Besides the fact he could easily just call her in to do so, if he didn't sign off on it then it is invalid. He's the king.