I'm leaning towards the baby solution. If I recall correctly, back in Chapter 1, the spell seemed to activate after Erin said she wanted to survive so she could find love and have a family of her own (shown with an image of her, her husband, and a baby). She has found love, but has yet to have children, which is the one unfulfilled element of her wish. I think Erin's mom created the spell to ensure Erin's future happiness, because she knew what a horrible life her daughter was going to get with the Samed family. Or maybe she saw the future and knew Erin's life would be in danger from Rowan, and didn't want her daughter's life to end so miserably. However, using a spell was super risky, which may reflect how desperate Sophia was. She pretty much had to leave Erin to the mercy of the spell and hope it worked out. :\ That's my guess, anyway.
So...in my opinion, Erin and Rowan need to get busy, hohohoho!