Part of what makes David and Steerforth's relationship "problematic," from a Victorian perspective, is its homoerotic subtext. In this exchange, Steerforth is apparently romantically interested in a (hypothetical) female version of David. The passage also underscores the idea that the friendship stands between David and adult masculinity by reinforcing his more "feminine" (that is, passive) traits: Steerforth's description of David's "sister" as "timid" and innocent is transparently a description of David himself.