Yes, the $19k tuition that she paid from the loans, is support she provided for herself. So, yes, you probably can't claim her as a dependent. If she is the sole borrower (the parent did not co-sign) then that is her money, for purpose of the support calculation. Scholarships are treated differently. That is third party support and not support she provided.
Back to your original question; is it worth filing? This year yes (any other year, maybe not). Since she can (most likely) no longer be a dependent, she is eligible for the $1800 stimulus/recovery rebate.
Grad students are not eligible for the refundable tuition credit.
There are two types of dependents, "Qualifying Children"(QC) and standard ("Qualifying Relative" in IRS parlance even though they don't have to actually be related). There is no income limit for a QC but there is an age limit, student status, a relationship test and residence test. Only a QC qualifies a taxpayer for the Earned Income Credit and the Child Tax Credit. They are interrelated but the rules are different for each.
The support test is different for each type. The support test, for a QC, is only that the child didn't provide more than half his own support. The support test for a Qualifying Relative is that the taxpayer provided more than half the relative's support.
