I'm a romantic at heart, so to me a collar would be worn as a sign of commitment in the relationship. Wearing one in play would not have the same meaning as one worn to show those who know, I'm "collared". NOw, does "she" think the same way?, if not then it has no meaning. So, yes I think it's when a "couple" find themselves at that place and time and have the mutual feeling of a collar that it takes on the symbolism just a thought take care