A good sister is more than a good friend. If she loves you, she would do for Allah’s sake, with no self-interest. When you’re with her, you won’t be hurt or ignored. She loves for you what she loves for herself.
She is always concerned about your hereafter and your own good, she will always remind you of obeying Allah. she always gives advice, shares her knowledge, keeps contact with you, asks about you and will always be there for you.
In this Dunya, she is a trustworthy and loving companion. In the Akhira (the hereafter), because of her love you will be shaded under Allah’s shade, in shaa Allah
The Prophet ﷺ reminds us of the importance of good company in this hadith (record of the Prophet ﷺ): “A good friend and a bad friend are like a perfume-seller and a blacksmith: The perfume-seller might give you some perfume as a gift, or you might buy some from him, or at least you might smell its fragrance. As for the blacksmith, he might singe your clothes, and at the very least you will breathe in the fumes of the furnace.” [Bukhari, Muslim]