I asked my surgeon how big one's gall bladder normal is, anyway, as my uncle saved a gall stone of his that they removed and it was golfball sized. Normally, he said, gall bladders are about the size of a smallish pear, so that made sense. None of mine, thankfully were that big. Your friend should know she's rarity, as my surgeon said he has done hundreds of these surgeries, and only once has he encountered a perforated gall bladder in all those years. He said appendixes are much more likely to burst than gall bladders, thankfully!