This is the thing, there are thousands of Nudi types, the basic physical characteristics of the Aeolidioidae family are seen by zonathid eaters, aiptasia eaters, coral eaters.....Yes it does look like similar to a Berghia Nudi, but it also looks just like types that eat Sarcophyton and Xenia, it looks like what it eats. The likely hood that it originated/hitch-hiked in is more probable than the OP getting lucky and a Berghia Nudi just happened to hitch-hike in. If you have a coral where the polyp head and tentacles look similar to the Nudibranch than I would remove the invert.