Originally Posted by OldKingClancy
She's not his mother. M doesn't stand for her name, it's just a title for the person in charge, hence why Mallory got called M at the end of the film.
Also nobody calls her mom, they're saying Ma'am. Trust me, I'm British.
Here is an excerpt from Casino Royale:
James Bond: I always thought M was a randomly assigned initial, I had no idea it stood for...
M: Utter one more syllable and I'll have you killed.