Do I have to open a separate account to do my daughters taxes

The TurboTax online editions can only be used to complete one tax return per account and User ID.  To start another online tax return you would need to create a new account with a new User ID - https://turbotax.intuit.com/personal-taxes/online/

Up to 5 User ID's can be associated with one email address

OR -

Use the TurboTax Free File program if you are eligible - https://freefile.intuit.com/
If you are eligible you can use the TurboTax Free File Program which is free to file both a federal and state tax return. The Free File Program edition is a full featured personal tax program and on a separate website from the TurboTax online editions.

 

To qualify for free 2019 federal and state tax returns with the Free File Program, you'll need to meet at least one of these requirements:

• A maximum 2019 adjusted gross income (AGI) of $36,000; or
• You qualify for the Earned Income Tax Credit (EITC); or
• You served as active duty military (including Reservists and National Guard) with a maximum 2019 AGI of $69,000 (you'll also need a military-issued W-2).

 

When using the online product, only one tax return can be completed with each account. 

 

You must open a separate account for your daughter. If she only had W-2 income and no other forms to enter, she could use the Free Edition. The same email can be used for the second account but the user ID and password must be different.

 

Here is what the Free Edition can be used for: https://ttlc.intuit.com/questions/1913043-is-turbotax-free-edition-right-for-me

The Free Edition described in my answer above and the Free File Program in DoninGA's answer are two different programs. Both are free. The Free File Program can handle many forms other than the W-2 but there is an income limit.