You could reply back and tell her now that you know more info about it, the machine is more valuable. Add $2000 to the price....
Seriously, stick to your guns and do not reply to her. There are those out there that do this to people. They sit in wait for people to be taken advantage of. I have had some replies with 'tone' from Ebay. I just hit 'delete' then send Ebay a remark about the replier. They want to know about those remarks!
Your machine is worth every penny and then some. My Ellegante would sell for 1500-1800 on Ebay. Full price was 6500, I paid 3500 3 years ago from a LQS. I wouldnt sell it for less than the 3500 today. Others may have different thoughts, but that is the value to me.