I feel that not being open and honest about this sleeping issue right off the bat is irresponsible. I would not appreciate finding out about this after I had already made an inquiry... it would put me off of her very quickly, mostly because her owner didn't tell me sooner.
In the current market, it is extremely unlikely that she will sell for so much. I was noticing that she was the most expensive horse for sale on that page... but some of the others looked like they had better movement and so on. Ironic that they weren't selling for so much.