How do you prepare for cognitive decline and the beyond?

Hi. My Mom has breast, lung and brain cancer and I am her primary caregiver.

She has had two bouts of pneumonia - both resulting in trips to the ER. On the second trip (just this weekend), she experienced a marked change in her cognitive abilities. She went from being responsive to basic commands and generally polite to confused, angry and mean-spirited towards me (and even the nurse). I thought this could have been a reaction to the antibiotic that she received, but the doctors said that was not the case (though when I read the medication warnings, increased confusion was one of them).

I also learned that the cancer in her lungs have spread and that she has lesions on her spine (in addition to breast tumors and brain lesions). I do not know her prognosis (have not spoken to her doctor), but obviously, she is not getting better.

She still lives at home (and I live with her), but setting aside the effects of the pneumonia and fever, her hygiene has deteriorated, she expresses intentions to do things - clean a room, drive her car, go to a store - but does not/cannot make an effort to do them due to extreme fatigue.

My questions: She absolutely hates it when I speak to her doctors - this sets her off more than anything - but I need to understand what stage she is in so that I can prepare emotionally and operationally for what is coming. Should I call them in confidence? I think they would understand and not share with my Mom that I called. (I have medical POA).

What can I read to prepare for what may come as her condition worsens? (though I pray that her doctors can stop the spread, but this latest news was a real blow).

What should I absolutely be sure to ask her / take care of before the confusion advances? (I have legal paperwork taken care of for the most part - there is one last document I need to get her to sign this week).

She is super-sensitive to talking about the future and does not like it when I bring it up. Should I wait for her to do so?

Finally, I am thinking about bringing in a home health care aide/nurse soon so that Mom gets to know and trust them if her condition worsens (and so that I have someone to help me manage through this). Does it makes sense to do this or should I focus instead on finding a facility (e.g., hospice care)? She would not want to leave her home, but it may come to a place where I cannot care for her.

Thanks everyone for your thoughts.

Grace