"Gift Tax" is somewhat of a misnomer. Even though a gift tax return may be required, very few people ever actually pay federal gift tax. The purpose of the gift tax return is usually only to document a reduction in the allowable estate tax exemption.
See https://turbotax.intuit.com/tax-tools/tax-tips/Tax-Planning-and-Checklists/The-Gift-Tax-Made-Simple/...
For 2019, a gift of more than $15,000 triggers the need for a gift tax return. I assume the "college fund" you sat up was a UTMA/UGMA ("she paid taxes on gains every year"). The money is legally hers, even though you are the custodian of the account. As such, a gift tax return is required if she gives the money back to you.
