凉情凉心菇凉百毒不侵
[liáng qíng liáng xīn gū liáng băi dú bù qīn]
It describes someone whose emotions and heart are 'chilled down', almost untouchable. 'Mushroom girl impervious to all poisons' might imply resilience against harm, betrayal, disappointment, etc., having experienced too much pain to care deeply anymore.