菇凉讲脏话是掩饰自己
[gū liáng jiăng zàng huà shì yăn shì zì jĭ]
Literally translated as 'the girl speaking obscenities is covering herself'. Here, it seems to express an idea that cursing could be the means by which the said girl hides her genuine self. It indicates some defensive mechanisms against vulnerability or exposure of real feelings