I think we might make some sense of Luna's behaviour with this.
Denial is the first of the five stages of grief. With the loss of SC, Luna's world became meaningless and overwhelming. There came a major gap in her life where SC used to be. She was in a state of shock and denial. She wondered if she could go on, and why even go on? The denial then started to fade, and as it did, the feelings she was denying began to surface
ANGER is the most common and recognisable part of the grief process. I think that Luna is here now. She has accepted the reality and the denial makes space for anger. Anger is the emotion she is most accustomed to. The truth is however, that anger is irrational and knows no limits. This is similar to denial in that it will extend to her friends and allies. Who knows, her brother, too?
Anger is a temporary strength. It is important for Luna to fully accept the anger, because that is the best way to let it fade away so she can go on to the third stage.
BARGAINING
DEPRESSION
ACCEPTANCE