ask her. it is doubtful that under any conditions Turbotax will allow you to access her account. if she used 1 account for your and her returns only the last one prepared is still there. the other is permanently gone.
if you can't get it from her, you can get a transcript from the IRS either by registering to get it online or filing 4506-T for a transcript or 4506 for a copy of the return.
https://www.irs.gov/individuals/get-transcript online transcript
https://www.irs.gov/pub/irs-pdf/f4506t.pdf IRS sends transcript thru mail free
https://www.irs.gov/pub/irs-pdf/f4506.pdf IRS sends you a copy thru the mail for $43.
