This was serena acting out, blowing off steam Like she always does.
blow off steam 乱发脾气
把多余的蒸汽放出来,就表示发泄咯。

I see my mom is sending in the big guns.  
big gun 有影响力的重要人物
我们说大腕儿,他们说大枪。

I should hear your father out before I end things.  
hear sb. out 听某人把话讲完

Come on. I bust you out of the loony bin.  
loony bin 疯人院

but the only way I'm going back there is in a straitjacket.  
straitjacket 紧身衣
也有束缚的意思,这里是说除非你们来硬的强迫我去疯人院。

It seems everyone's favorite party girl fell off the wagon and landed in rehab. Good luck getting a lohan-dle on things, s. From the looks of it, you've got a lot to recover from.
fall off the wagon 毒瘾复发
lohan-dle 林赛·罗韩式的(反反复复进戒毒所)


She worms herself out of everything, and I needed to make sure that there was one more nail in her coffin
nail in the coffin of 致命一击
一般会说final nail,棺材盖上的最后一颗钉子,比喻意义为最后的致命一击

That's a pretty tall tale from a not too reliable source.  
tall tale 离谱的故事

The past stays in the past. 
过去的就让他过去吧。


时尚装扮 地道口语 尽在绯闻女孩华丽专题