Did you save the return as a pdf file when you were done? You should always save it as a pdf so you have a copy of it. Did you give her a printout copy for her records? Or you will have to get the AGI from the IRS.
You can request a transcript from the IRS
https://www.irs.gov/individuals/get-transcript
How to find last year's AGI
https://ttlc.intuit.com/community/agi/help/how-do-i-find-last-year-s-agi/00/25947
