Pete,
The seller told you upfront it was a sanke with quite a temperament. As a buyer you are entitled to ask as many questions as you wish before committing to a purchase. Once you decide and unless there is a health issue it doesn't seem fair to ask for a reimbursement.
As far as trying to calm her down I wouldn't cover her enclosure up (unless she is hurting herself when striking the glass). She is obviously afraid of you, the more she sees you and realizes you are not a threat the sooner she will tame up. Wear a sweatshirt for a couple of days and then leave it in her enclosure. This will make her get used to you faster. It will not avoid striking from the distance but it will make her feel more comfortable once you grab her and she smells your skin and clothing. To remove her from the enclosure, always cover her first with a sheet of paper. Only then try to grab her from under the paper while you hold her down gently from above. Don't use cloth as she might strike it and get her teeth entangled. Always hold her with both hands one one foot from the head (to limit striking range), the other holding the heaviest part of the body. Try to avoid her seeing you place the food in her enclosure, this will only make matters worse as she will associate food with your presence.
Hope this helps and you are able to tame her down.
Regards.
