My daughter is a full-time student, works a part-time job and earned $2800. We claim her as a dependent and her 1098-T. Why is she not getting a refund of her taxes?

Did she get a W2 for it?  She should get all the federal income tax withholding back.  Just not the SS or Medicare in boxes 4 & 6.

She can still file a tax return to get her taxes back.  She must file for herself, but where she enters the number of "exemptions" she MUST enter zero (0).  (She may need to override the automated form.  See right-click menu for that field.)  Usually a person enters one exemption for him/her-self, but since YOU can claim her, YOU include her as an exemption.  Also YOU must include her in the list of dependents, even though she files her own tax return. If one social security number appears in two tax returns, the IRS software "captures" the number of exemptions on each return to compare and ensure there is no duplication of claiming the "exemption."  Your daughter is the "dependent," and your tax benefit is the "exemption."