Forget the gala itself.
They weren’t invited to S.W.O.R.D.’s space committee meeting.
That ones simple: the Kree half of the Alliance are the faction that slaughtered them (probably summoned by Teddy’s grandmother)
Also Black Bolt is kind of considered a bit of a war criminal for causing the Fault
The Inhumans still ruled the Kree and were quite welcome in the new Galactic Council when they were ruling them so even if Black Bolt is a problem sending another would be ok.
My idea, the Inhumans are in a self created solar system of 10 planets, that is right in between the space that makes the Kree Utopia and the Kree/Skrull Alliance. Acting as a buffer state basically as part of their treaty.