Termination or Miscarriage
"So, she's a stolen soul, your wife isn't a soul for this generation. Her life wasn't registered so the moment she gives birth to her first child, she returns to her world and waits for her time. That's the fate of a stolen soul." Those were the facts about Mona's life according to the vision from the past and the troll's help.
"Now, if you are thinking that there's a way to make her stay on Earth after she gives birth. Um, sorry for crushing you but there's no possible way because she's stolen and she's being looked for so God made that curse on stolen souls so they return on their own.
And at their young age, he sends his servant to bring all stolen souls so she must have encountered something scary at her young age seeking her soul back but was saved so she has to face it now."