I have a friend who is a jewellery designer. She makes cool laser cut necklaces with bits of gold and silver leaf in (check out her shop on Etsy, there’s lots of cool stuff there). Recently she started to notice other people copying her designs. Understandably annoyed, she confronted them, but go little in the way of a response. So, she got back to work and changed her designs and tried something else, something new and cool that other people wouldn’t have thought of.
It’s well known that constraints feed creativity, but I think innovation can create constraints, which can in turn force you to need to be more creative. Rosa’s jewellery being copied, was crap in a way, but equally it also validates her ideas: people like them so much that they want to copy her.
Software projects and startups are the same. How many projects have you worked on where another company took what you did and built on it? How many times have you felt cheated because someone took your idea and succeeded?
On the internet there is no “your idea”.
As soon as it’s out there someone will like it and copy it. If they do then, great! It means you have something other people want. Now you have to keep improving it and changing it to stay ahead of the pretenders. Now you have to be creative.
James Jeffries' Blog 
Someone I know works in the music industry and he told me that when he started out recording music and songs, he’d burn the original copy to CD and post it to himself by recorded Royal Mail delivery with a cryptic message on the back of the envelope (so he knew what was inside). Once he received it, he’d keep it unopened and if he believed anyone copied it, he had the package ready and dated (and recorded by Royal Mail) to take to court so it was proven he had the idea first.
I wonder if this would work in a similar way for your friend? Especially if things are done in a unique way.