Ivette's reaction to Janie reveals her PERCEPTION that The Worm would prefer she keep a promise to a friend over winning money.
I'm gleaning that during Ivette's upbringing, The Worm enstilled a VALUE along the lines that people are worth more than money; don't break a promise to a friend, loyalty above personal gain, etc. There is also that situation with her brother that may also enforce this ...
Ivette sincerely believes her family would support the decision she made to keep Maggie.
Now, The Worm is not going to stop loving Ivette, and probably respects "the heart" and motivation surrounding her decision. In real life, it's honorable to choose a friend over money. It would be interesting to know what Ivette thinks of her mother's BB interview after she sees it!