That’s the second time you used that retarded analogy.The law states that if you shoot a man falling from a skyscraper and the bullet kills him, you are still guilty of murder. Doesn't matter he was seconds away from crashing into the pavement and dying. Its still murder. Plus opioid overdoses happen almost always instantly, GF was still conscious and functioning although sluggish.
What happened here is not anything like shooting a person jumping off a skyscraper.