Is it permissible for me to marry a girl whose mother was nursed by my mother's brother's mother?

If the mother of this girl nursed with your maternal uncle (your mother's brother) five full nursings from your grandmother, from whom your mother also nursed, then this girl becomes your maternal aunt's daughter through nursing. Marriage to a maternal aunt's daughter is not forbidden, because she is not among the unmarriageable women mentioned in the Holy Quran or the Sunnah (definition). It is not a condition for the two mothers to nurse from the same breast at the same time; what matters is that nursing occurred from the same breast, even if the timing was different.