It's my sister.
例句:
Who help you with your study?
谁帮助你学习?
It's my sister (who help me with my study).
是我姐姐(帮助我学习)
如果句子想表达的是“她是我的姐姐”则翻译为“She is my sister"
希望能够帮到你!
She is my sister.
但是如果是在大电话的时候,就应该用第三人称
She is my sister.
补充:She is my elder sister. 她是我姐姐。
She is mu younger sister. 她是我妹妹。
She is my sister.
Is my sister