Congrats, Eve, she's a stunner! Happened to me when I tried to get an EE foal for quest and accidentally bred an EWW TB colt who also happens to have the genes to produce apricot! Can't wait for him to grow up next month.
Yes, Frame x frame, and White x white (not splash white), can result in lethal white foal. When breeding your horses the game will show a message that says the pairing resulted in LW and the foal passed. There will be no individual horse page for the foal, so you cannot see it.