Help find out why my sister passed

I am creating this go fund me to help my nephew cover the cost of a private autopsy for my sister. She passed away unexpectedly on December 24th. The coroner did not request an autopsy so my nephew has had to schedule a private autopsy to try and give us answers as to why this happened. She had a knee replacement surgery on Friday the 23rd in Tennessee. I was with her during this procedure and the surgery went well and she was up and walking within a few hours after surgery. She got released and we made our way back to Indiana so she could recover there with the help of me and my parents. It was a long trip and I'm sure was not easy on her but we got to Indiana safely unfortunately, Christi did not wake back up on Saturday afternoon. Her son lives in Hawaii so he has to travel quite a ways to be able to come and take care of things and find some kind of closure. The private autopsy is a huge expense alone and with him having to travel and be away from home and work for an unknown period of time, it will be very costly for him. Losing your mother is hard enough so I am just trying to help ease the burden for him a little.

Thank you in advance to all!