I am trying to file a return for my sister, who is not my dependent. How do I set up an account in her name with my contact info?

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://turbotax.intuit.com/personal-taxes/online/

https://ttlc.intuit.com/community/using-turbotax/help/how-do-i-start-another-return-in-turbotax-online/00/25596

Your sister needs her own contact info, which could be your mailing address.

See 1040 Third Party Designee if she wants your name on her tax return.

IRS recently told me  that Designee is only good for one year after filing.

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