Tā zǒngshì bì kāi zhège huàtí, yīdìng yǒu nányánzhīyǐn.
She always avoids the topic — there must be something she can't bring herself to say.
Tips
history
From the late-Qing novel 《二十年目睹之怪现状》 by Wu Jianren: nearly every household has 难言之隐, and most of them, the narrator quips, are caused by the womenfolk. The phrase entered common usage from late-Qing fiction.
usage
Commonly preceded by 有 (to have). Used sympathetically — implies the speaker doesn't want to press the person further. Also used euphemistically for health/financial problems in advertising ("某些难言之隐").
