I am so sorry to hear about your mother. I know that this is very hard for you and your families.
Have her doctors given you any prognosis? Stage 4 is very serious, and you need to urge the doctors to be very frank with you and with your mother. You need to be realistic about her situation in order to get her the best care possible. If the doctors agree, it may be time to call in Hospice. So many patients do not receive Hospice care until the very end, when it is too late to do much good. IF she is eligible, they can be a great help in pain control and in avoiding the mental side effects of pain meds which she seems to be experiencing. And if she gets a lot better, Hospice can release her from their care...it is NOT a final decision. And Hospice personnel can be a great help to the entire family.
If Hospice is NOT an option, please ask for a consultation with a palliative care specialist. These are physicians who specialize in pain relief for just the sort of situation your mom is in. There is much that can be done, if the right medical help is available.
Wishing you all the very best
Sara Anne