Some people are just carriers and the virus can sit idle for years AFAIK.
The questionable part though is that even if the virus is idle in a carrier\'s body it can infect and kill others. Such as her children during her pregnancy.
But anyways I am not sure about the full details so I cant comment. Perhaps she got infected afterwards and the current explanation on how she got it, is probably a suspicion than a proven fact. Perhaps she got it later from something else