Powell is now fighting the Omaha school, arguing that her tuition was covered by scholarships and that federal loans wouldn't need to be repaid in that amount. She also notes she was kicked out even after undergoing months of counseling, spiritual training and mentoring insisted upon by the school following her initial suspension.
"I shouldn't have this debt hanging over me from a school that clearly didn't want me," the 24-year-old said.
The university insists that the $6,000 bill covers federal grants and loans that, by law, must be repaid to the federal government because Powell didn't finish her final semester. School officials declined to discuss specifics of Powell's case, citing federal student privacy laws, but through a public relations agency said it would provide Powell official transcripts and transfer her credits.
Powell is skeptical. She noted that nine months after she was expelled in January 2012, the registrar's office denied her request for her transcripts because of the bill, though she eventually received student copies of her transcripts.
Grace University's code of conduct for its students is strict: No kissing, no prolonged hugs and certainly no premarital sex. The school even monitors students' television habits, forbidding HBO, MTV, Comedy Central and several other channels "because of the values they promote." The rules are laid out in a student handbook and signed by students every year.
"No one was more surprised than me," Powell recalled of her relationship. "I had been very religious since I was a small child, and that did not fit in with what I thought I believed."
It's not unusual to see gay and lesbian students disciplined or even expelled from private Bible- and faith-based colleges, but Powell's case is unusual, said Ken Upton, an attorney at Lambda Legal. The national civil rights organization helps gay, lesbian, bisexual and transgender people.
"This particular case is unusual because there's this fear that they might not release her information and they are demanding payback," Upton said. "We don't see that very often. Usually, the school's just glad to be rid of them."
In response to questions about the case from The Associated Press that included Powell's financial aid letter, the U.S. Department of Education said in an email Friday that the issue of whether Powell owes money is between her and the school -- but "it's not at all because of federal rules."
The department said it would need to analyze any case to determine if a school had violated federal discrimination regulations. But it noted that educational institutions controlled by religious organizations are exempt from some federal requirements that might conflict with the organizations' religious tenets.
Grace and other private colleges that accept federal student aid -- sometimes called Title IV funding -- must abide by the Civil Rights Act that forbids discrimination on the basis of race, national origin, sex, age or physical handicap. But sexual orientation is not included in that list.
"There's a long history of institutions of higher education that are faith-based participating in Title IV programs without having to compromise their institutional statement of faith or institutional statement of practice," said Ronald Kroll, director of the accreditation commission for the Association for Biblical Higher Education, which includes Grace University.
As required by the university after her suspension, Powell said she promised not to engage in sex and completed months of church attendance and meetings with Christian mentors, spiritual advisers and other groups. She was then readmitted, only to receive a letter days later from the university's vice president, Michael James, revoking her admittance.
James wrote that her re-admittance had been based on professions she made to various faculty and staff that she would change her behavior, but that "the prevailing opinion is that those professions appear to have been insincere, at best, if not deceitful."
"I was livid," Powell said. "I had done everything they asked me to do. I drove over to my mentors' house and just bawled my eyes out."
Powell legally married another woman in neighboring Iowa in December, but the couple still lives across the border in Omaha and has found support online. Her wife, Michelle Rogers, posted a petition on change.org asking the university to drop the tuition bill.
"Being kicked out of school for being gay would have been awful enough, but Danielle's nightmare didn't end there," Rogers wrote. "In addition to being expelled, school officials revoked her scholarships and are hounding her for $6,000 in back-due tuition for the final semester -- which she was never allowed to complete -- that her scholarships would have covered."
As of Friday, the petition had been signed by more than 35,000 people.