No. You can just go in and change it. However, it will reject if you're trying to claim dependents that your mother in law has already filed for. You may need to mail it in if you want to include all of your dependents.
Don't amend if:
- You haven’t actually e-filed or mailed your return yet. Just open your return and make any changes, and file when you're ready.
- Your e-filed return is rejected. Just make your changes and then resubmit or mail your return.