What metaphors are used in The Mill on the Floss by George Eliot?

In Book V, Maggie and Philip meet secretly. During their time together, Maggie returns a book she'd borrowed from Phillip, saying she disliked it because the author, like so many others, had the fair-haired girl win over one who was dark, like Maggie. Philip tells her that one day soon she may triumph over her fair-haired cousin Lucy in love. This annoys Maggie, who had been speaking metaphorically and does not like to think of being Lucy's rival. Philip tells her he loves her, but she says she could never upset her father by returning that love.