Marian and Laura are foils for one another. One represents the Victorian ideal of a beautiful and virtuous woman, the other strays from most of what is expected in a woman's appearance and behavior. Despite their closeness and love for one another, this pair of half sisters seems to be a pair of opposites in most aspects, especially when it comes to beauty, independence, and femininity.
This antithesis is no secret to the sisters themselves. Marian describes their differences to Walter the first time she meets him:
Except that we are both orphans, we are in every respect as unlike each other as possible. My father was a poor man, and Miss Fairlie’s father was a rich man. I have got nothing, and she has a fortune. I am dark and ugly, and she is fair and pretty. Everybody thinks me crabbed and odd (with perfect justice); and everybody thinks her sweet-tempered and charming (with more justice still). In short, she is an angel; and I am—
Laura may be richer, prettier, and sweeter than Marian, but she is hardly a character in her own right. She also never seems to actively participate in the plots or narration of the novel. Although nearly all that Marian and Walter do throughout the novel is for Laura, Collins does not give her much of an identity besides being Walter's damsel in distress and Marian's foil.
By extension, Anne is an additional foil for the two sisters. She resembles Laura and dresses like her, but is often described as her shabbier and more sickly-looking understudy. Eventually it is revealed that the resemblance between Laura and Anne is far from a haunting coincidence—they are half-sisters as well. Laura has a half-sister from each of her parents, each of whom serves as her foil.
