Out of curiosity, how did Carol remove the moonstone from Karla when it's not something she wears or carries, it's something she physically absorbed into her body years ago.
Karla had to use all her considerable psychological knowhow on the previous Moonstone so his self image was so lousy that he didn't feel he deserved the moonstone any more and his body reflexively rejected it. I can't see Carol managing that.
I'm also unconvinced by the end A) How did Carol know that Karla had, presumably, guilt over her mother? and B) Someone as smart and calculating as Karla would probably be able to deduce what trigger point someone like Carol (Who is smart, but no in Dr Karla Sofen's league as a psychologist and therapist who KNOWS how people's minds work) would assume was the cause of her problems and go there.