Close synonyms include girl, miss, missy, young woman, fille. Each sense on this page lists its own synonyms, because a word with several meanings rarely has one substitute that works for all of them.
Is young lady a common word?
young lady is banded "Rare" — specialist or archaic — most readers will not have met it. The band comes from how often the word appears in a large corpus of everyday English, not from an editor's impression.
Definitions, synonyms and semantic relations for young lady come from Princeton University’s WordNet. Commonness is measured against a corpus of everyday English. Full sources and licences.