I am so sorry to tell you that not only do we not know who her parents were, we don’t know who she was.
The name “Matilda de Normandie” got put into a profile that originally, and rightly, had no name, because someone misread the history in the Overview and confused the wife of William the Conqueror (Matilda of Flanders) with the wife of the commander of the ‘Mora.’
I blame the writer of the passage given in the Overview; the pronoun “his” refers, at one point, to William the Conqueror, when the subject of the sentence was Airard, the commander of the “Mora,” and if one doesn’t already know the history, that is a pretty confusing sentence.