Hi! Happy to assist!
Since this is a 2021 tax return, I am thinking that the main difference in the refund amount might be due to stimulus payments that were sent out in the beginning of 2021.
If you claimed your daughter on your 2020 return, IRS would have sent you the stimulus payments. When your daughter filed on her own, I am assuming she entered she did not receive the stimulus, because practically you did.
Another issue with stimulus is that if your income was over the certain amount, based on your filing status, you would not qualify for stimulus for yourself or your dependents (in case you never received any). But if your daughter files on her own with little or no income, she does qualify for it, based on a single filing status and saying she cannot be claimed as a dependent, even though she was supposed to be your dependent.
We would need details in order to give more precise answer. You might have lost certain credits by having higher income than your daughter, like earned income credit. Also, when amending the return if you already filed, the refund amount on 1040X is in addition to what it was already received.
