Did Meg mean to shoot Christine?

CONSIDER:
Meg kidnapps Gustave, Christine's and The Phantom's son, and almost drowns him. When Christine, the Phantom, and Madme Giry arrive to save Gustave, Meg, saying she feels unwanted points a gun at her head, But when the Phantom tells her the most obvious thing that she will never be like Christine, instead of just admiring her friend, because of the latter fact or shooting and killing herself, because of the latter fact, she shoots and kills Chistine! This sounds like premeditated murder. Look how the scene is staged in the video below this information. Also she is bipolar and has these symptoms:

1. Feeling unusually “high” and optimistic OR extremely irritable
2. Unrealistic, grandiose beliefs about one’s abilities or powers
3. Sleeping very little, but feeling extremely energetic
4. Racing thoughts; jumping quickly from one idea to the next
5. Impaired judgment and impulsiveness
6. Acting recklessly without thinking about the consequences
7. Delusions and hallucinations (in severe cases)

So... HOW responsible is she for her actions?