Geraldine is the daughter of the Imperial Archmage and she was one of the participants in the race to land George’s hand in marriage. While she didn’t land the big prize, she did get the first runner up, in that she has been welcomed into the Regens household as one of his mistresses.
She has also been appointed Minister for Magic in the External Empire. This appointment was the reason she was granted an artistocratic title, and thus the also the reason why she can accept a mistresses ring while retaining her own status as a free person rather than a dependant.