James,
KNowing your sister is walking with Jesus is a comfort for sure. Rest on that knowledge.
My uncle told me last I saw him that "even death is God's perfect healing" ---to be with Jesus and no longer in pain. He lived that to the end.
He suffered with bone cancer, went into remission and this was when it returned.
Prayers that the Holy Spirit cover her up with Grace, peace that passes all understanding and strength to live on faith. Prayers for the same for her loyal hubby, her kids and all the rest of you who love her.
Keep the Son in your eyes!