The narrator has already described Linda as the "true daughter of the austere republican." Again the implication is that Republican Liberty has more affinity with the ideal of lawful society than with the ideal of classless utopian liberation (Giselle).

I sense perhaps another, less abstract reading to this paragraph, in which Giorgio is feeling alone and abandoned by the engagement of his best-loved daughter. Note that "the man at her side," though obviously signifying Nostromo, could technically refer to Giorgio as well.