Why she's the killer: It's obvious that Claire isn't being completely honest with her son. After she suspects that he is lying to her about his relationship with Ava, she orders campus security to put extra surveillance on her son. When Taylor and Nolan meet in the abandoned cabin on the other hand, they seem pretty adamant about proving that the campus is using their technology for just that. Perhaps Claire catches wind of what her son is doing and decides to put a stop to it once and for all.
Why she's not the killer: Nolan is her own son. It seems unlikely that she would go that far to keep her shady business with the college a secret.