What exactly were her injuries from the bus accident? Also, in the movie, it shows she lost some of her toes. What caused the gangrene? It then implies later she lost her leg. Was that also from gangrene? Did she have any mental problems? Did she and Diego ever stop cheating on each other?
See here (“Her spine was broken in three places, her right leg received 11 fractures, her right foot was crushed and her pelvis was broken in three places”). She got the gangrene in that same foot later in life, and had to have the leg amputated below the knee to stop it spreading. I think there were multiple factors: pre-existing withering from polio, the injuries, and the many subsequent operations, would have presumably contributed to poor circulation in the foot; and I don’t suppose her bedbound state and being a heavy smoker helped.
The litany of injuries leaves out the gruesome detail that the pelvic and spinal fractures were caused, at least in part, by being impaled with a piece of the tram’s railing through her vaginia and out her side. She wrote on at least one occassion that the accident had taken her virginity.
The woman endured enormous physical suffering. To my mind, it’s not bizarre that she acted a little bizarre as a result.