小宅女外贱内骚
[xiăo zhái nǚ wài jiàn nèi sāo]
Combining traits of introversion ('a girl who prefers staying at home') with hidden desires, this phrase includes somewhat vulgar and pejorative elements, especially in its second part. A more tactful description might refer to someone shy but with inner passion or someone whose public image doesn’t quite match what they keep private. Please note the term chosen can be sensitive.