水性杨花 -------- unstable as water

例句：
A: It's said that the man divorced his wife, didn't he? How come?
据说那男子和他的妻子离婚了，是吗?怎么回事？
B: Yes, they got divorced, for his wife was unstable as water.
是的，他们离婚了，因为他的妻子水性杨花。

同义词：
as changeable as the moon
A woman's mind and winter wind change off