True, but don't forget that Caster is a romantic at heart, and someone who takes betrayals very badly. Cruel as she is, harsh as she is, she doesn't mind a valiant would-be hero rescuing a damsel (after Kuzuki changed her outlook), and equally loathes oathbreakers like Archer (from her own past). She would feel sympathy toward betrayed, idealistic girls like Rin.
I honestly believe she respects Rin quite a bit.