Were they uploaded into folders ?
What do you mean selling your stuff for years ?
Are the images the items for sale or are they images of the products you have for sale ?
If the latter bearing in mind you cannot stop her thieving them without an excessive amount of work and no doubt very slow and lethargic assistance from greedbay is it really cost effective to spend a lot of time trying to stop her.
Ok she is using (thieving) your time by thieving the pictures but she is also taking a lot more of your time trying to stop her which is virtually impossible on greedbay.
She can probably damage you more and reduce you as competition by getting you stressed and wasting your time, business can be dirty and some sellers have no scruples, ethics or morals, just greed at all costs.
In which case she could win here by driving you into the ground mentally.
I would consider whether it is worth the effort, think, which affects your bottom line more her thieving or your time being wasted ?