Who is Eragon's mother?

WARNING: SPOILERS AHEAD FOT THOSE WHO HAVE NOT YET READ "ELDEST" AND/OR "BRISINGR"

Selena, or the Black Hand. She originally fell in love with Morzan (the rider who betrayed the others) and would do anything for him to gain his love. He saw this as an advantage because not many others have such faithful and reliable servants, and used her as an assassin, where she used the title of the Black Hand. Eventually she gave birth to Murtagh with Morzan as his father. As Murtagh tells Eragon in the first book, Morzan threw his sWord at him when he was just a small child.

When Brom infiltrated Morzan's castle as a servant, he met and fell in love with Selena. They kept their relationship a secret, and as soon as Selena found out that she was pregnant with Brom's child, she left for her hometown of Carvahall to stay with her brother, Garrow. She did not want the pain that Murtagh went through at the mercy of Morzan's sWord to also happen to Eragon. So he was left there, and (as you may or may not know,) he grew up and by some bizarre act of fate, magic, and circumstance, he was given a dragon; and with that, the responsibilities of a dragon rider. Now, I could go on and on about the ties between Eragon and Brom, Saphira and Thorn, and how Saphira's egg came to be in Eragon's possession, but that's not the point. At the end of the second book, Eldest Murtagh tells Eragon that they're brothers. Now, that's true; to some extent. Murtagh and Eragon are HALF-brothers. And in the third book of Brisingr, it is finally revealed that Brom is Eragon's father, and he is given a portrait-like thing of his mother.