Hi, she does not even have to copy them it is extremely easy to link to your imaging host without copying them.
And I have said before more than once now, if it can be displayed it can be copied.
I am not going to say how and encourage others but basically you cannot stop somone from using your images or even your listings except by getting ebay to pull them and I think you already know how difficult that is.
I have also said before that the Auctiva protection will only stop the laziest copier.
You are better off getting on with selling and providing a superior service than your image thief because it is likely she can't be bothered to do that properly either. Customer loyalty can be the deciding factor on who does best.
To have a niche market you have to have a unique item and from what I see it needs to be a talent to create art forms from base materials. Anying that requires selling goods made by someone else will always be competitive.
So you are better off being superior at supplying the goods and stop being so concerned about the image thefts, you cannot do anything cost effective about it and the Auctiva protection will not help you.