Like Mary, she is bold, a little dangerous, sexual, but in a way you can't really place your finger on, and above all, controversial.
In iconography, Mary Magdalene's attribute (an item or feature that identifies her as that particular saint) is an alabaster jar or box. Chloe's, given her penchant for constantly changing style, would be more difficult to spot, but if pressed I would say her long, blonde hair, one of her few constants.
Charlotte Gainsbourg would be the Virgin Mary. More conservative, traditional, but deeply, almost fanatically revered.
And Lou Doillon would be John the Baptist. Wild, untamed, natural, disheveled and underrated:
Her attribute would be the wonderful way in which she pulls off hats: