Does my daughter need to file her own tax return for unearned income only?

No, your daughter must file her own return for the reason noted below.

In addition to being a qualifying child dependent, the child has to meet the following conditions:

• The child’s only income is from interest and dividends, including capital gains distributions and Alaska Permanent Fund dividends.
• The child’s gross income for 2023 is less than $12,500. This limit increases to less than $13,000 for 2024.
• The child is required to file a return for the year.
• The child does not file a joint return for the year.
• There were no estimated tax payments for the child for the year (including any overpayment of tax from the child’s prior year return applied to the current year estimated tax).
• There was no federal income tax withheld from the child’s income.

For more information you can review this link:  Should I include my dependents income on  my tax return?

Q. Should she file her own return with this, or can it be added to our return since she is still a dependent and this is her only income?

A. Because of the type of income, she must file tis on her own return.  But it turns out, that's a good thing.

Q. Since she will be taxed at our rate I'm not sure what the difference is? 

A. She gets a $13,850 deduction before tax kicks in. 

Scholarships are a hybrid between earned and unearned income. It is earned income for purposes of the $13,850 filing requirement and the dependent standard deduction calculation (earned income + $400).  It is not earned income for the kiddie tax and other purposes (e.g. EIC).  For grad students and post grad fellows, scholarship, stipend and fellowship income is earned income ("compensation") for IRA contributions.