The Kering family hadn't told the public about Arix's identity before, because they feared it would put her in danger. The Kering family's daughter, the only Supergiant+ in the Alliance—these two identities would make all the powers of the galaxy want to get her.
So, in the eyes of most people in the Alliance, Arix was still that girl from Planet Waste, Arix Thalis.
At the family banquet of the Kering family, only the top families of the Alliance were present. They might know Arix's true identity, but in terms of her true power, the Kering family only claimed she was a Supergiant.
The five noble families knew Arix's real strength, but they understood the Kering family's concerns. Therefore, they also kept silent in agreement.
So, Arix never expected that one day she would become famous because of a scandal with her own brother.
Creation is hard, cheer me up!