1.She is really a pill, spending whole day harping and complaining. 
她真烦人，整天唠唠叨叨的。 
pill本意是指“药丸”，在此喻指“讨厌的家伙”，因此也就有了“烦人”之义。 

2.I give him an inch, and he takes a yard. 
他太得寸进尺了。 
这句话表示不知分寸，爱占便宜。也可说：“I gave him an inch, and he wanted to take a mile.” 
如：Jerry keeps asking me for help. At first I helped because he was new here, but now... I give him an     inch,and he takes a yard. 
杰瑞总是让我帮忙。一开始我觉得他是刚到这儿的就帮了，可是现在……他太得寸进尺了。

3.She must be having a few buttons missing. 
她肯定是脑子有点不正常。 
此语中的buttons原指“纽扣”或“按钮”。此语主要用来表达“神经失常”、“行为古怪”以及“头脑失常”之类的概念。 
如：She must be having a few buttons missing. That's why it's useless to argue with her. 
她肯定是脑子有点不正常。这就是为什么我说你跟她理论没用 

4.You are plain doormat. 
你真是个受气包。 
doormat 是个合成词，由door(门)和mat(垫子)组成，意指放在门口处供人“蹭鞋”的门垫，是个专门供人“踩”的东西，跟“    受气包”的概念是不是很贴切呢?