Would you rather:
A: Your close friend & coworker marry your favorite brother...only for their marriage to directly result in both of their deaths a few days later?
B: The woman you believe you caught sleeping with the love of your life before you ever got a chance to make a move on him, marry your less beloved brother, whom you have no real excuse to exclude from family events, and as a result, your children will be calling this woman you hate "Aunt"?
Lucky Elayne doesn't have/get to pick.
By letting her know her kids are Rand's ... the guy who wouldn't sleep with Berelain? Or maybe she just ends up claiming Mayene as an Andoran/Cairhien province just to piss her off