If my mother breastfed my aunt once, would that turn her into my sister from rida'a? and their children become my mahrem or not?

asalamu'alaikom wa rahmatu allah wa baarakatu, I have a question that I couldn't find the answer. Let me explain. My mother breastfed my aunt when she was a baby. That makes her become my Rida'a sister ? . And if so, are her children my mahram or are they still my cousins? thank you for taking the time to try to explain this topic baaraka allahu fikom.