Lex captured Kara and Lena before session 6. pain and blood.

"Lena? Lena it's me, it's Kara, your friend..." Lena made no sign that she knew her, Kara knew she did not recognize her, but she had to try... Lena raised an eyebrow, "I know who you are, but, you see, my slaves usually bow to me. so, bow to your queen, Kara..." OR Kara sent to AU time line to save Lena's life. she meets a cruel queen instead;

based on this pic of Lena reaching her hands to Kara 6x20 ending.