一意孤行----go one's own way

例句：
A:The wayward girl is a great trouble to her parents.
那叛逆的女孩让双亲非常头痛。
B: Absoultely. She is always going her own way.
是啊，她总是一意孤行。

同义词：
take the bit in one's mouth/teeth
take the law into one's hand