Hi Kijsa
I had this exact same problem last year and was really upset by it, people trying to re-create my designs down to small details, to the point where their listings could have been mistaken for (sorry- but less well made versions of) mine at a glance. The best advice that I was given is to feel bad for them, they are obviously lacking the innovation and creativity that you have. You will always have new ideas and be evolving and they will be stuck in a rut. Plus the copies never live up to the originals.
Evolve and move on, that 's what I did. The anger just spurred me on to make better things.
Sorry this happened to you!