re: your number 2:
If, and I still have some issue with this story....
In a hot, sunny car interior, the peroxide may have decomposed in the back seat, releasing free oxygen and creating an oxygen-rich environment inside the car. Then the tip of the ciggie flared up. H2O2 will not decompose to anything flammable, but as we all know, excess oxygen impinging upon an already-ignited something will cause a flare-up of some kind.
Just being a little nitpicky on ya. Same overall result you cited.
She was driving an Austin Mini, and had to open and then close the door to get in and drive away. That alone should have cleared out a significant amount of any concentrated oxygen that had built up inside the car. And cars are nowhere near airtight to begin with, so that should limited the extent of the build-up.
Her father is quoted in the Daily Mail article saying “It was her day off, and she was making her way home to do her mother’s hair, so she had her equipment bag with her and would have been carrying hydrogen peroxide in a small amount.” And she was a “mobile hairstylist”, so it doesn’t sound like she was operating a large scale hair-styling business, involving purchase of large containers of concentrated hydrogen peroxide.