Well... well I guess this could still be a serial murderer who lugs her victims' bodies with her wherever she goes. But since there haven't been any stabbings yet, I'm going to guess it's Tommie's great aunt Tilly, who's going to crash at 3G for a while and hamper Tommie's dreams of stardom with her cheap luggage-toting frugality and common sense.
There is also still an outside chance this could be Santa. Much like Zeus and Hermes, who disguised themselves as weary travelers to test the compassion of mortals, Santa wears many masks to find out if we're good or not. Don't be tricked, Margo!