Is my female cousin considered my sister through breastfeeding if my full sister breastfed from my mother along with her, and is it permissible for me to marry her according to Islamic law?

The sister who asked the question was nursed by the mother of her maternal aunt's daughter, so she is her sister by suckling, and thus she is forbidden to all who were nursed by her maternal aunt. As for the questioner, she was not nursed by the mother of her maternal aunt's daughter, so she is not her sister, and there is no harm in her marrying her maternal aunt's daughter.