Lois wears a jeogori and leggings as her formal attire; rather than a dress. This both reflects her heritage and keeps with her tomboy image; in typical depictions, tomboy loathe wearing skirts.
The Parasite suit reflects Ivo. His using others for his power and ruining himself, only to blame others for his faults.
Lois likely reclaimed her lost apparel from evidence collected by the police when they searched Ivo Tower.