Can I file a 2 separate personal returns for myself and my mother sharing one log in and one email?

[JulieS]

No, you can't file two separate tax returns with the exact same credentials, but you can connect two accounts to the same email. 

Each 1040 account needs a unique user ID, but you can use the same email and phone number as contacts on two different accounts. You can also use the same password for both. 

[xmasbaby0]

When you use Online TurboTax, you get one return per fee.  Each return needs its own account and user ID.

  If you use the same account and user ID for a second return, you overwrite the first one and lose it forever.

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