Gyuri with Younha, SJ Ryeowook, Leeteuk
Hara with 2PM Wooyoung
Jiyoung with 4Minute Sohyun, SJ Leeteuk
Nicole with Infinite Woohyun
and I think Seungyeon said that she is friend with After School Uee but I'm not sure cause she doesn't talk much about her celebrity friends
oh and I think all Kara members are friends with Spica Boa