Meaning:
“红茶” means “black tea,” and “女生” means “girls.” In contrast to the term “绿茶” (lǜchá; green tea), which is used by Chinese netizens to refer to girls who appear to be nice and demure but are in fact merciless and manipulative, “black tea” is used to describe girls who are cheeky and don’t bother to hide their not-so-nice intentions.
Example:
A: 丽丽为什么和她男朋友吵架？
Lìlì wèishénme hé tā nánpéngyou chǎojià?
Why did Li Li squabble with her boyfriend?
B: 有个红茶女生明知道他有女朋友还约他一起看电影，他居然赴约了。
Yǒu gè hóngchá nǚshēng míngzhīdào tā yǒu nǚpéngyou hái yuē tā yīqǐ kàndiànyǐng, tā jūrán fùyuē le。
There was this cheeky woman who, with clear knowledge that he is seeing someone, asked him out on a movie date. He did go with her!