I'm no medical expert so take this with a grain of salt, but high blood pressure (which was mentioned as something this woman had) is a sign of preeclampsia, a very dangerous medical condition. Combined with the stress high blood pressure puts on the heart and the fact that preeclampsia can cause aneurysms to pop, that would explain it. Being fat also makes preeclampsia more likely and even more dangerous. Preeclampsia is my very unprofessional opinion.