I am so, so sorry for what you and your Mum are going through. I have not gone through anything like this. I don't know what I would do either.
It's a terrible situation. I wish I knew how to help.
I'm sure what you want right now is some practical help. I wonder, do you think it might help to talk over your feelings with someone before phoning your Mum? Just to air the feelings, express them and then be able to focus on allowing yourself to hear your Mum, and to tell her those things which are important to say, It will still be very emotional, very hard, but you might feel a little more prepared to carry these feelings if you talk to someone first.
Beyond Blue has the phone Counselling Service, and the Chat Online service as well. I don't know how to make links to those here, but you'll find them at the top of the page.
Or, the hospital, they surely have a social worker who might be helpful to both you and your Mum.
I'm sorry I don't know what else to say. I can't imagine the depth of pain you and your Mum are in. You have both been through so much.
My warmest regards,