Break down of this Japanese sentence into words
I am trying to better my Japanese vocabulary by reading children's books. I have started with "Let's be friends again (Bokutachi mata nakayoshi)" by Hans Wilhelm. I have the English version as well so I know the meaning of each sentence. However I am trying to break it down into the various words to build my vocabulary. However I am stuck at this sentence:
いもうとったらいやになっちゃうんだ
The English version says "my little sister was a real pest". I can only identify "imouto" as "little sister", I have no idea what the other words are or even where they start from. For example, I don't know if the next two words are ったらい and やになっち or った and らいや etc.
Kindly help me out. Thanks!