If you were to go into the hero editor, you would see the description of Pender. It reads that no one knew where she came from, and the few who asked did not survive the confrontation with her.
Now if you were to read Omarn’s description, it says that he was an apprentice - but to whom?
My theory is that Pender was Omarn’s master, and taught him everything she knew. However, the ogre invasion happened, and Pender retreated into the mountains, living a life of secrecy. This explains how she knows more spells than Omarn, since she practiced her magic then. Your hero then went into the Mountains and found Pender.
And the rest is history .