If you already have the TurboTax download on your computer you can actually do up to 5 free e-files on that program.
This is one very nice feature on the download program as you can do multiple returns on the one program you purchased.
You would just go to your existing program and click on File to start a new return. Then start your mother's return.
Return the program you bought as it is not needed unless you plan on loading it to a different computer as only one TurboTax program can be loaded on each computer.