Sometimes an Amended Return cannot be Efiled, even though the original return was.
Has she already received her Refund from the original return?
She may want to try Efiling her amended return after the current tax filing season is over.
The amended return does not 'catch up' to the original return and correct it. It's processed separately and can take several weeks to process.
Here's more info on How to Amend Your Tax Return and Can I Efile My Amended Return?
Thank you. We e-filed about 3 weeks ago and realized we forgot a 1099. She has already paid the amount due with the original return, but now she owes an additional amount. She doesn't have a checkbook so filing and paying electronically would be so much easier.