Welcome to the group Josh, hope to see you here often. It's who we are.
As far as Cheryl Andrews, I don't believe for a minute she betrayed the group she believed in, but after her bizarre discovery she made performing an autopsy, she went to Germany to report it, and was arrested. And who authorizes her release but Homer B. Pettey. We all have seen in the episode Skull and Bones where he worked/lived. I believe she uncovered something about the group where she saw its dark side, and it was the group that killed her, to keep her quiet. I believe Cheryl was forced to betray Frank, possibly protecting the life of a family member. In the synopsis of The Hand of...., it states ~
As I stated above, I believe she found out something, or things, about the group, and they killed her for it. She was Frank and Peter's friend and they all had a mutual respect for each other. I am sure Peter knew why she was killed, and had nothing to do with it, but also had no choice but to remain silent. Or, he was quietly seeking answers himself.
The group had a dark side and that side would do anything to keep from being exposed.
Maybe some of the questions from these episodes were going to be answered in season 4, and sadly we only have virtual seasons after 3. I don't believe there was a mistake in the writing, but I do believe that the writers of many episodes left us with questions on purpose, and some may never be answered. Two excellent episodes.