The extortion charge could be reasonable, but the California Penal Code sections 530.5 and 653m charges are ludicrous: 530.5 deals with identity theft for taking out loans and such and 653m deals with telephone harassment, this is neither.
If you want to see another example of prosecutorial overreach, you should read up on Bond v. United States, which was recently argued before the Supreme Court of the United States. Bond was charged with violating chemical weapons treaties for using chemicals to kill her husband's mistress' lawn (amongst other things).
I don't mean to take a position on whether the federal government can use the Chemical Weapons Conventions to prosecute someone for trying to poison another, but there's a big difference between trying to poison another person, and trying to poison their lawn.
Your last point speaks to Bond's intent, which makes this an interesting narrative, but she was not charged with attempted murder.
Bond was charged with possessing, transporting, and spreading the chemicals, which have been classified as toxic (along with vinegar and chocolate). This is because the state police and prosecutor exercised prosecutorial discretion by not charging Bond, and the federal government has no jurisdiction over one person "trying to poison another".
edit: though intent is unimportant, it has been alleged that Mrs. Bond caused a rash on the victim, which is relevant, because this would be evidence of "harmful effects on plants or animals".