Quack exorcist trying to steal the insurance money or actual real shaman called for the unusual asshole death?
I'm guessing on it being a scammer, and as his mother hurting and the family money getting robbed would trouble MC I believe best GF will do something about it.
Now about childhood friend, she is a truly good girl, as much is clear, but to the eyes of a murderous youkai how she will appear? A thieving cat? A possible romance threat? A insect buzzing close to her man?
She made clear from the get go that tehy are together, so I don't see CF trying to steal him, but this chapter was made to make her awaken her feelings towards him for real, no more simply good friendship.
We can only wonder if Yandere knew what was happening and didn't care.