NO, do not use your account! Unless you are filing a Joint return with them.
Online is only good for 1 account and 1 return. 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
Or use the Desktop program. The Desktop program can do unlimited returns and efile 5 for free. And you can use any Desktop version, they all have the same forms. So you could use a lower version than you might need in the Online version.