I have been part of an artisans cooperative for 20 years. Several years ago one of the other photographers started mimicking my images and product lines. The other members and the customers are confused as to whose photos are whose. She continues to do this even though has been told to stop. Is there anything I can do about this? I have lost a lot of sales due to this duplication. Thank you.

What you are describing could be copyright infringement. You have rights in your photographs under copyright law that include the right to copy, publicly display and make "derivative works" of your photographs. Someone can't make a substantial copy of your photographs without your permission. This includes taking photographs with substantially identical settings. If people are believing that the other photographer's works are your works because they are substantially similar to your works, then you may have a claim under copyright law. You have to register the copyright with the United States Copyright Office before you can enforce the copyright.