I had the same issue on Mercari and the guy had an arguing match with me too and clearly it was in bad condition. I rather people just be honest ... They just get so defensive.Well the seller is already messaging me complaining that the photos showed the conditions.. Even though I also asked her to confirm conditions.
Anyway, I told her I'm not here to argue but please sell this to someone else. She will get her bag back in better condition since I tried to clean it as you suggested and it looked a bit better. Gah