Pepsi & drugs don't mix!!

That is a lot of Pepsi, but not a huge amount of caffeine. In the UK the caffeine content of Pepsi Max is substantially lower than the US 42.6 mg/12/oz. So in a day she would be ingesting about 950 mg. and that would have been over a long period of time, That is close to the level that would produce symptoms of caffeinism in a non-habituated user. If she were doing that every day she would likely have been pretty tolerant, and the amount delivered at one dose would be limited. The lethal dose (LD50) of caffeine is 150-200 mg/kg, so unless she only weighed 5 kg (11 pounds) and drank it all at once her chances of dying from caffeine would be a lot less than 50-50. Her chances of dying of water intoxication or a ruptured stomach might be better.  Fluoxetine has a lethal dose estimated at >1200 mg which would be in the range of 60+ 20 mg capsules...not something that you would reach by accident. A potentiating cross reaction of caffeine and flouxetine is not likely to explain why the combination would have killed her, unless she took a deliberate massive overdose of Prozac. The article notes that she also did alcohol in large amounts, and there may have been problems with her liver which prevented detoxification. Fluoxetine overdose is associated with seizures and obtundation, so it is possible that aspiration asphyxiation was involved, but the specific findings are not reported in the article.