Okay, let's get this over with...
1. It's pretty obvious that Gigi Caldwell is helping the murderers (AKA: Red Devil(s))
2. Boone is obviously one of the murderers.
I suspect that Gigi is calling Dean, because Dean Munsch has murdered her husband, Mr. Munsch, due to his relationship with his "Beatles 101" student, Feather. Feather has been under false arrest, while Dean is the real killer, and out of the asylum and prison.
Can't you guys notice the music on the background when Gigi looks at Grace with that evilish look?
You guys have to look into the small details and the tinier details as well.