In the Halo universe, it is well know that Miranda is the daughter of Captain Jacob Keyes. In the recent Halo: Glasslands it is made obvious that her mother is:
Dr Catherine Halsey
However, when was it mentioned before this, if at all?
The entries occur in her mother's journal, included with the Halo: Reach limited edition. Among other things, it documents her growing feelings for Jacob (Keyes), and the eventual birth and separation of Miranda and her mother.