steal my thunder

I get really frusterated when people try to steal my thunder, or just get thunder i wanted.. For instance, make and sell things on Etsy, and I liked having my own special things I can make, and her having her own special things she can make.. but now she is making the things I make. I should not be so frusterated, but I am, and I don't like it, but there is not much I can do about it. Just keep doing what I am doing I guess..