A PLUS loan is irrelevant*. Loans are just a source of support. A PLUS loan means your ex is providing that support. BUT, In the case of a "Qualifying Child" (QC-a full time student under age 24): who provides the support is not relevant. Note that the support rule is not that the taxpayer provided more than half the support, but only that the QC didn't provide more than half his own support.
Where the child lives is the relevant issue ("but she lives with me ").
*When the student takes out a loan totally in his own name (no parent co-sign); that support is considered provided by the student himself. If that amount of support is more than half the student's total support; then neither parent can technically claim the child.
