I did get it when reading the book but I actually found it weird. Specially because Goldilocks is not strictly a fairy tale, which would have been more understandable coming from Mab.
"Goldilocks and the Three Bears" (originally titled "The Story of the Three Bears") is a British 19th-century fairy tale of which three versions exist.
I think Lara’s problem is that she desperately wants to be a mother, but I suspect female Whamps are even less fertile than the males, and the two men she would consider as father material are the two men who won’t sleep with her.