My wife says that she was nursed by her grandmother for half a year?

If your wife was suckled by her grandmother five full sucklings before the age of two, she becomes a daughter to this grandmother and a sister to her sons and daughters. If this grandmother is also your grandmother, then your wife is not permissible for you, because she is either your paternal aunt through suckling or your maternal aunt through suckling. However, if your wife's grandmother is a stranger to you, this does not affect the impermissibility of your wife to you unless there is another reason.