I filed a return for my mother-in-law and now I want to file my own. Every time I sign back in her name and info comes up. How do I get a new set of documents for myself?

Use a different account and different user ID so that you do not overwrite your MIL's return and lose it forever.

https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-online/00/25596

You have to set up a whole new TT account for yourself, with a different User ID and password.