I actually addressed some of theloop's concerns in an earlier post - but I didn't like the way I wrote it so I wound up editing it. The editing was taking so long that I finally said screw it
, and I deleted my entire post. I will attempt this again.
IF theloop hired this "competitor" to help with certain aspects of his event (ie. create brochures or flyers or banners or whatever for the event), the competitor would be considered theloop's "employee." As employer, theloop would hold the copyright in any works created by the employee while the employee was under theloop's employ, barring any agreement to the contrary. The works created would be considered "works for hire."
IF this was the situation, then this competitor/employee would not be able to use, copy or display the work-for-hire works without permission from theloop, the copyright holder. This would apply to photographs of the created works, as well, as photographs of the works could be seen (potentially) as derivatives.
Although nothing legally prevents this competitor from stating that she worked on the event and did suchandsuch while under theloop's employ, she cannot claim the copyrights in the works, or exercise any of the rights that come with having a copyright (ie. copying, publishing). Those rights belong to theloop. Nor can this former employee/competitor legally claim the event was hers if it wasn't.
Although the situation described sounds more like unfair business practices, misrepresentation and/or fraud than an infringement matter, both copyright and trademark laws could play into it - depending on the exact business arrangement the competitor and theloop had, and depending on what exactly is displayed and said on the website.
Justalayman said that a review of the website by an attorney would be necessary in order to determine what legal action can be pursued against this competitor, if there is any, and I agree. If there is a legal action to pursue, I agree with TheOcculist that a cease and desist letter could be the cheapest and easiest way to resolve the matter.