Rafaela was hoping that enough of her older sister Luciela's human mind remained that they could Soul Link back up and try to hopefully undo Luciela's Awakening back into a Claymore from being an Abyssal One.
And Luciela's human mind did seem to return, with Abyssal One Luciela crying about/for her beloved younger sister Rafaela. Unfortunately, her Abyssal One/Yoma mind shortly took back over, causing Luciela to start talking about conquest and killing/finishing off Isley.
Realizing it was impossible to save (de-Awaken) Luciela, Rafaela then kills Luciela.
Yes, Rafaela hug-crushed Luciela to death (you can see the limp hand of Luciela, signaling she was killed).
But, read on to find out what else Rafaela did (AFTER killing Luciela) causing something to happen... *grins*