Emphysema related death

I had posted a question related to my friend's passing who had emphysema. However at that time I didnt know a great deal of details as I didnt have access to her full medical records, CT scans and X Ray. Now after reading them all, I believe there's a need to put the correct question. Im sorry for the community members having to read some of the stuff twice.

Kingman, AZ. She was diagnosed with emphysema around 5 years prior. We didn’t think much of it and despite trying her best, she couldn’t quit smoking. For last 2 years while talking, she would start to say things that would make no sense. We used to think it was probably lack of sleep (Now I realise it was lack of O2). She would also stay awake for days at a time. In October 2017 she was admitted after she could not find 911 buttons on her phone probably due to lack of oxygen. Then she was admitted again in December. Last time she was admitted was in Feb 2018 after she fell down. At hospital she had respiratory failure and was put on ventilator. She was found to have pneumonia, DVT, PE and Enlarged right heart ventricle (RV/LV ratio of 1.3, and P-BNP values >23000) and 'moderate pulmonary hypertension' (peak right ventricular systolic pressure is 63 mmH). So yeah her heart was weak. (Could sending her home without O2 lead to heart failure?)

She became better and was taken off the ventilator after 4 days. She later developed an abscess measuring 5x5x5 cm in right upper lobe where she had pneumonia. She remained very weak and required a walker to walk. Her last CT scan reads “severe centriloular emphysema throughout both lungs” and “Severe diffuse emphysematous changes in both lungs”. Her PE seemed to have dissolved after 2.5 months of anticoagulant treatment as there was no update in diagnostics about it in further records.

Her P-BNP values got better and a month before her passing were around 5000. She remained at the rehab till 25 April. A decision to send her home was made suddenly after her insurance expired. She was released within a day of notification.
On 25th, she was sent home. At rehab she had been on supplementary oxygen varying 3 to 1 litters. But at the time of her release they measured her levels and told me that they were higher than 88% hence she didn’t require supplementary oxygen, and she was sent home without that. I was in another country unfortunately and due to such short notice I could not come. I requested hospital to send her with oxygen but they didn’t agree. She was supposed to call me once she reached home. When I didn’t get a call from her for few hours, I called 911. They found her on the floor passed away, next to her walker, face up and hands on the chest.

Between the time when she was supposed to call me and the estimated time of death, I believe it took her 2.5 hrs to pass away after collapsing.

No autopsy was performed and cause of death was mentioned just COPD.
She was the closest person to me in my life and my life is destroyed and is meaningless after her. I’ve tried to recover but not knowing WHAT caused her death and IF I could have saved her had I called 911 a little later. Would she have been on the floor calling for help.. These questions have been eating at me from inside out. Ive read so many research papers and gone through her medical records thoroughly to educate myself enough trying to answer WHAT caused her death and HOW she passed away, how her final moments might have been. But I lack the experience and all I could think was either a respiratory failure or a heart failure. But as Ive read that respiratory failure is triggered by something like infection etc, but as she was free from infection then, I don’t know if that could have been the cause.
I would REALLY appreciate if, on the basis of your experience, you could give me a vague idea as to what might have actually killed her? Perhaps, you could help take me out of my misery.

She also developed lower extramidy edema and DVT snd PE as a result of emphysema. What is its relation with Emphysema?
I have all her detailed medical records and CT scans in case you wish to take a look. I could share a link.
And I do understand that a definitive answer as to what might have happened to her is impossible to get. I just wish to get a probabilistic and most likely thing which you believe might have happened as per you.

Also if you had to rationally put (I know it depends from person to person etc) but how can I establish how advanced her condition was and how long would she have lived before being completely devoid of carrying on basic tasks?

Thank you!

Ive uploaded few of her CT and X Ray images. Ihavent been able to make much sense out of them If you could please tell how severe the emphysema appears in CT, I would highly appreciate. Secondly. I showed the X Rays to someone and they told me "she has hyper expansion of her lungs pretty severely it appears. Cardiomegaly too. Her bronchus is pulled to the side I'm sure making it even more difficult for her to breath. Likely from hyperinflation. Infiltrates and bronchi full of fluid. " Though didnt provide what all that means and their impact on her health or contribution to her passing.