Louisa Jacobson’s Met Gala Monday started bright and early at 4 a.m. The actress is currently filming the fourth season of “The Gilded Age,” and arrived at The Mark Hotel for gala prep straight from the series’ backlot set in Long Island City, N.Y. “ It’s where we built a fake 61st Street and Fifth Avenue. So I went from fake Fifth Avenue, to real Fifth Avenue,” Jacobson said on Monday afternoon, as her stylist Edward Bowleg arranged a tray of jewelry nearby in her suite. “I was walking along 78th and Fifth, and there was this big huge mansion on the corner, and it was reminding me of Bertha’s mansion in the show,” she added, calling out the central matriarch portrayed by Carrie Coon. “It’s nice to continue on this show after having built relationships with all of these actors, and have their characters build relationships with each other over the years,” Jacobson added.…