@Divian16 So sorry for your loss. First of all, did your mom use TurboTax to file her tax returns? Without her account and user ID you will not be able to access her returns on the TT site. TT has lots of security in place to prevent that.

If you do not have that information, you will have to go through some steps to get the returns. Are you the executor? Do you have legal authority to obtain her documents?

Here is a copy of an answer given by TurboTax to a question similar to yours:

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 the following documents:

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!

Perhaps you will want to start by contacting Customer Support:

To call TurboTax customer support

https://ttlc.intuit.com/questions/1899263-what-is-the-turbotax-phone-number

They are available from 5 a.m. to 5 p.m. Pacific time Monday - Friday.

**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**