Jaime found this and passed it along:
It’s the blissful expression on Betty’s face, combined with the sheer terror on Archie’s, that really sells the last panel. Her parents are away on a weekend vacation. Jughead is in Shelbyville at a chess tournament. Veronica is distracted, thanks to tipping off Reggie that Archie would be “otherwise occupied.” Moose and Dilton are useless. Archie is all hers, and as she lies glibly to Ronnie, she knows at last the sweet taste of triumph.