I think you mean "yeojadeuleun" vs "yeojaga" (여자들은 vs 여자가). This is referring to women in general, so it uses the "eun"/"neun" (은/는) particle. We'd use the "ga"/"i" (가/이) particle if we were referring to a specific group of women, in which case we'd use 여자들이 (여자가 would refer to one specific woman).
소녀 would be the direct translation of girl, but it is apparently not often used in spoken language.
Naver translate includes girl as a translation of 여자. Woman is nevertheless the translation used in most example sentences and is to be considered the primary meaning.
So, I guess in the end it will be a matter of subjective decision by the course developer once you've submitted as a report using the flag icon.