I agree with you entirely. We don’t know much about Dr. Vogel’s pass except for the fact she had a husband. In the last episode, when Hannah asked Vogel what push her to choose that field in psychopathy, she mentioned that it was an incident in her past that made her choose it.
I say to myself, what if Dr. Vogel had a son who is a psychopath and had kill his father (Dr. Vogel’s husband)? Now, that’s a very good reason to study psychopathy, especially if you got someone in your family who is a psychopath. What if Cassie’s boyfriend happens to be her son?

yeah, she has a connection and I think she’s more involved then we realize but she’s not doing the killings herself. I think she didn’t know who it was at first but has found out and it’s Cassie’s bf who is actually Vogel’s son. Now that she knows she’s not out to kill the Surgeon but assist him in some way.

If it’s Vogel, then why would she intentionally go to the trouble of placing jars of brain on her front porch and have a frightened look on her face when she knows that no one is watching her? Also, why would she frame Yates, just to put herself within seconds of death. If it wasn’t for Dexter she would have died that night. The fact is that although she has an obsession with serial killers, her personality doesn’t fit that of a serial killer. There are a few candidates, but the clues point to Cassie’s boyfriend or possibly even Vogel’s unknown husband. Otherwise they are completely doing a personality reboot on a current character which would just be way too throwed off.