This passage struck me too, but the Omniscient Narrator tells us that Mrs. Smith's "elasticity of mind" is "from nature alone", apparently not a matter of will-power or "right thinking" on Mrs. Smith's part. The ON greatly admires this quality but doesn't feel that other people can imitate it if they don't already have it. It's a very un-Victorian attitude, actually, which is why it struck me. Twenty-odd years later, the attitude would be that you should be able to develop *any* virtue if only you tried hard enough!