"Try to think about the nicest thing you can imagine!" "Death."

A female patient we have who is suffering from lung cancer with liver metastases is mumbling and crying.
I don't have to be visionary to see that she is dying.
Her skin is so yellow, if it wouldn't be so fucked up and sick to compare her to this, I would say she looks like a Simpson. It smells like death in her room. She is soaked in sweat and I'm trying to cool her face with a wet towel.

"I want to die.. I want to die.. Please, let me die." She cries from time to time.
I ask her: "Are you afraid of dying?"
"No."
"My colleague gave you some pain killers a few minutes ago, try to close your eyes, to relax a little bit and to wait until they work properly. Think about your most beautiful memory. Do you have kids?"
"Three."
"Try to think about them. Or try to think about the nicest thing you can image."
"Death."
I can't help her, I can do nothing for her. I don't know what to say.
I sit on her bed for a couple of minutes, caressing her shoulder until she sleeps or loses conscience or whatever.
I leave the room quietly.
I remember something a very calm and thoughtful colleauge said to me once:
"This is a long way and everybody has to go on his or her own and it is different for everyone.
Sometimes they can go easily and sometimes it's hard for them."

Edit: She died yesterday a few hours after we talked.
My colleague I. said that from time to time she wanted to die and then suddenly she was asking for chemo.