So many questions about anoxic brain injury

Hello everyone, I have some questions. My wife suffered a severe and traumatic cardiac arrest from which she did not recover, resulting in anoxic brain injury due to oxygen deprivation. She experienced repeated episodes of stopped breathing followed by restarting, both at home, in the ambulance, and in the emergency department. We are unsure of the exact duration of oxygen deprivation, but it was clearly long enough to cause brain damage.

Following a six-day stay in the intensive care unit, she was placed in a medically induced coma and subsequently taken off sedation to assess neurological responsiveness. All she did was have myoclonus jerking which is the subject of my questions.

They did a brain MRI on the day the cardiac arrest happened which indicated:

"IMPRESSION: 1. Extensive restriction of diffusion of the gray matter involving the basal ganglia, caudate nuclei, bilateral temporal, occipital, frontal and parietal white matter, hippocampi, and cerebellar hemispheres

➡️Findings are compatible With global anoxic brain injury"

My issue is that she had myoclonus jerking which appeared as though she might still be inside. That's what I'm having a hard time with. The jerking at first included her eyes opening, and she gazed upward. She exhibited a pain response in one hand and one foot approximately twice daily. She exhibited fixed pupils and failed to respond to verbal stimuli. She seemed to do the myoclonus jerking when irritated but that's just my opinion on what was happening. The environment was noisy; I played music for her, engaged in conversation, and made physical contact to attempt to soothe her. Her heart rate went up and the jerking started again, basically. Like, how am I to believe she was "brain dead" (sorry idk how else to word that) when she seemed responsive? The doctors said she was gone, but I'd get other opinions from the nurses. Was she really gone? Did she hear us? It's driving me crazy. It's really getting to me.

I would appreciate your thoughts.🙏 Thank you for your patience with my lengthy and perhaps less-than-polished post.

***edit. I have no idea how besides grief brain fog but I somehow forgot to mention she passed away after those 6 days in the ICU. We made the difficult decision to donate her organs so that her gift of helping others would continue.