I believe this person is manipulating the eBay system.
Not only she claimed it doesn't fit (although we've sold 5 more before that, all with the same description) but she claims a sewing shop at Nampa, Idaho, more than 3,700 miles !! far from buyer has ruled that this attachment is a high instead of a low shank. Determining this is just impossible from far since the part that goes on the machine needs to be compared with a known one to determine what is what or just attach on a machine. I doubt that shop would ever say that, firstly because the attachment is for a low shank and secondly they don't even have one in their hands while we have many. Spent more than 8-10h in 5 different days to first show with video how she could attach it and then after filing for Item not as described, to resolve return and then a negative feedback left from her stating i "lied" !!!
Just after receiving this attachment we made a video unpacking and installing, without any cuts or edits. It only took 10" seconds to install it from 1':30" to 1':40" in the 2:30 long video. eBay support was very helpful and understanding, so they removed the negative feedback and suggested to report her which we did.
Since her behavior was puzzling i googled her and found an other seller had issues too, so here i am reporting her for this uncharacteristic behavior trying to smudge a 100% positive feedback of ours.
Sad we had to resort to such actions but it's better to help innocent sellers from dangers like that than stay silent.