She stay quiet because thousand of things are running in her mind which she decide not to say because it won't make a difference anyway..
She behaves wierd because certain things made her like this!
Some may say her an introvert
Some may say her a wierd girl
Some may demean her silence as her attitude
And honestly she is not bothered about the whole world all she want is peace within her soul.
She is lost..still finding her way..still finding her own self..