I lost my Daddy to lung cancer on March 23, 2009. He survived only 1 month and two days between diagnosis and death. My mother is currently on dialysis, but her complications are such now that she will not survive long, either. I am the youngest of their six children. She is also in the hospital.
You're in a very hard place right now
Please know that right now, things are a valley of shadow, but God is there with you all, including your mother. Even though things look as though they are viewed through a veil of pain, God is with you all on the clear side of the veil. While your heart is breaking, God is still catching every tear from you, and mourning with you.
To everything, there is a season, and it it tied to every purpose under Heaven...A time to be born, and a time to die. It's not our place, but God's, to know and orchestrate those seasons. Even though we feel so lost, confused, and tortured, God is still in control over everything which is happening. He's watching over your mother, sweetie.
I cannot tell you why my Daddy suffered so much before he passed, nor can I tell you why my mother is suffering so much right now. But I can tell you this...While death feels so close, the Father is closer. Trust Him.
Your mother may be sleeping, but you can still talk to her. I know I did to Daddy right before he passed. I didn't think he heard...But then, he smiled. Morphine blunts pain, but there's debate on whether it blunts cognizance. Don't be afraid to speak, and say the things on your heart. Let her know how much you love her, how much you care. Let her know the things close to your heart. She needs to hear it, and you need to know she had the opportunity to hear it. It's part of a process.
God bless.