Miss Charming is "unnaturally buxom, in her fifties, and sported short, bleached hair" (4.37). She's also the comic relief of Austenland. This woman can't use British slang to save her life, and her idea of a pickup line is, "Won't you show me how to use your mallet against the balls, Colonel Andrews?" (13.18). "Charming" is clearly meant to be ironic here.
To boot, Miss Charming pretends to be twenty-two years old, which highlights not just her own foolishness, but that of Austenland itself. It's a fantasyland, where women's dreams come true, albeit only for the three weeks they are there. But the main difference between Miss Charming and Jane is that Jane is looking for something real amidst all the role-playing. Though she takes her time at Austenland seriously, Miss Charming's just looking to have a good time playing this old-timey love game.