When Mama Elena dies, tita got rid of her duty (or that was her thinking) and how you can tell in the story Tita feels completly free to love Pedro, free to do what ever she wants to do since she knew him. But that´s not true, her duty still there, why? because she was destined to serve her mom not to marry, not to have a romance. When she supposed that she was pregnant (you know the reason), there's come Mama Elena to remind her that duty, obviously she got mad for what Tita did, she's angry and tells her that.
