Is marriage permissible with the daughter of a maternal uncle if her mother breastfed his brother fewer than three times?

It is permissible to marry the daughter of your maternal aunt ( بنت الخالة) unless there is a suckling relationship between you that prohibits marriage. This would be if she was suckled by your mother, or if her mother was suckled by your mother, or if both of you were suckled by another woman. Your mother suckling her brother does not affect this.