Trying to file a free tax form for my 16year old and turbotax keeps defaulting to my finished return. how do I get around this and create her own account?

Whatever you do, do NOT create a second return in  your same account.  That would overwrite yours and make it unrecoverable.

See this FAQ on how to start a second return online.   
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The Answer below also has info on the 2 free products--regular Free Edition and the TurboTax Free File Program.   If your child decides to use the TurboTax Free File Program, you can just go that website and create the child's User ID and account there.  If you create the child's User ID at Online TurboTax, then child will not be able to log in at TurboTax Free File Program without doing a formal switch.