There is something not quite right about this story, and maybe there is an explanation that just didn't make it into your post. Why would somebody go out and spend $2700 on something they don't know how to use, let it sit for a year, not open the software that was purchased, and then sell it for a fraction of the cost? Are you certain you did not get a true steal? Is the receipt in the same name as the person you bought it from, or do you only have her word for it that it is her receipt?
Here is a story to ponder. We had a 3-month old macbook stolen last fall. Thief sold it on Craig's list, told the purchaser his mom was a teacher but didn't "need" the computer any more. The buyer believed that story. He knew enough to get past the firmware password, saw plenty of evidence that the machine was owned by a school district (as he later told police), but he thought the tale told by the thief was plausible, so he felt justified in wiping out the hard drive and reloading the OS. Of course he told the police he was happy that the macbook was going back to its rightful owner, but personally I believe he knew full well he was handling stolen property and thought he could get away with it. Oh, the kid sold it to him for $200. Moral of the story - don't believe the stories that online sellers tell you.
If it was me, and her story is actually true, I would offer to teach her how to use a mac, so she could actually use the machine she probably spent her entire tax rebate or stimulus check to purchase.