Starting another return for another person

Yes, with TurboTax Desktop, you can e-file up to five federal tax returns and up to three states.

Refer to the TurboTax Help article How many tax returns can I file with TurboTax?

Thank you for that confirmation. Now, how do I start the second return without losing any of my information?

Save your return and make sure it is named something you won't get confused with other tax returns you will be preparing.   Then close your return.   Go to the main File menu up top, and select Start New Return and enter her information.   Be sure to save that file, making sure to name it something specific to her.   You can go back and forth between returns by choosing Open Return and selecting the tax file you want to work on.   How do I get started with TurboTax Desktop?

Actually with the Desktop program you can do unlimited returns and efile 5 Federal for free.   The rest you can print and mail.   To get to the menu items like File - Save go way up to the Apple bar at the very top.