After you file

So sorry for your loss.   Did your sister use TurboTax for her past returns?   If so, getting in to her account will be complicated, but you may be able to do it.  Here is a reply from several years ago to a family member with a similar issue:

Filing for relative who died

Hello @nardit1, I'm sorry to hear about your loss. I understand that this may seem like a lot to get into an account but we must take all due precaution to ensure the protection, privacy, and security of customer account information. We wish to make sure that the data your sister-in-law entrusted us with is protected. 
You will first need to fill out an Email Change Request: https://ttlc.intuit.com/questions/1899319 
In addition to your own photo ID, you must include one of ...

• A copy of the Death Certificate – The name of the surviving spouse will need to be matched to a Joint E-filed Return in our system
• A court order issuing Power of Attorney for the deceased and IRS form 56. (required for non spouse)
• A court order marking them the executor of the estate and IRS form 56. (required for non spouse)

  These additional documents may be included with the initial scan of the Photo ID.
  You will also need to print and mail the return and include IRS Form 56. 
  I hope this helps! 

  Answered by TurboTaxGabi