A loan (probably a zero-interest one at that) will be senior in priority to trade liabilities. In any case, it's unclear from the article if Fiorina's campaign paid her loan back in full, or only in part. I don't trust the WaPo to report that kind of detail accurately in a hit piece.
Also, I found this tidbit interesting (emphasis added):
That sounded like quite a lot of money to me for bulk mailings. In fact, it seems to be. From
this link, I calculate $13,506.89 all-in (including the cost of the mailing list and the actual first class mailing charge) for a large coated, brochure (8.5"x14"), with full color on both sides. And the price Mr. Seaton charged was 5 years ago (during a recession by the way). No doubt there was a little padding in the price to account for the credit risk, which is known to all to be terrible for a losing campaign.