Canon has now established that she was the younger sister of a Count Vorrutyer and so probably Ges's sister; extra-canonically, Lois has said she thought that was true. We know about her affairs from Aral's own lips, but we have never learned her first name. We've also never learned Aral's brother or sister's names--I don't think we even got Aral's mother's first name until A Civil Campaign.

Lois has said that she hates making up names, and I think names are part of her general philosophy of not committing to points of canon that don't directly affect the story in progress, so I'm not really surprised that the first Lady Vorkosigan doesn't have a name.