meli Sonko is a phrase from an example sentence in Toki Pona: The Language of Good. It is intended to mean "Chinese lady". The word Sonko is a place name for China, tokiponized from 中国 (Zhōngguó). However, the phrase can more immediately be interpreted as "lady named Sonko".
For ‘Chinese lady’ (meli Sonko), many people find it clearer to say meli pi ma Sonko or meli tan ma Sonko or meli pi kulupu Sonko. This avoids misunderstanding it as ‘a woman named Sonko’, because the primary interpretation of ‘[noun] [Name]’ is ‘a [noun] named [Name]’.