The local Fire Marshall needs to have a fire education session with the OR teams. *Heat, oxygen, fuel.
"Let me show you something!"
We have inservices about fires during surgery quite often. Surgical fires are an uncommon but not rare occurrence. Fortunately, they are typically extinguished before any harm is done to the patient. Lot’s of heat sources in the operating room these days. For example, we use fiber optic cables to deliver light to surgical telescopes [arthroscopy and laparoscopy scopes mainly] and the light from these is intense enough to catch the paper drapes on fire.
Then there are lasers, electrocautery units and etc.
My best guess is they didn’t let the skin prep dry on this lady before they used the electrocautery. It is alcohol based. A spark would ignite it easily and create a flash fire.