i want to set up and have a separate turbo tax account for my mother on my computer how to not default back to main account

You can use the same email for 5 accounts and returns.

You can start another return in TurboTax Online by:
Logging out if you are in your account
Choose what TurboTax Online product you want to use for the second return
https://turbotax.intuit.com/personal-taxes/compare/online

Create your account screen
Set up a new login for the second return
Start working on the new return

You can start a new account and create a new User ID on this website, just click on Sign up to start - https://turbotax.intuit.com/