Is it permissible to marry a female cousin (daughter of a maternal aunt) if the questioner and the female cousin were both nursed by another maternal aunt who is not directly related to the female cousin?

What is prohibited by lineage is also prohibited by fosterage. So, whoever is suckled by a woman becomes her son and the son of her husband, the owner of the milk. If you and your maternal cousin were both suckled by the same woman, she becomes your foster sister, and it is not permissible for you to marry her. However, if it was her sister who shared fosterage with you, and not she herself, then no state of prohibitive kinship is established between you, and you are permitted to marry her. The prohibition is established by five full sucklings.