Takes more than one person to constitute a conspiracy. You still ignore the fact that she didn't do anything to the woman but spray pepper spray in her car. That isn't attempted murder. Attempted kidnapping, yes. And I'll even go so far as to say that the circumstances don't lend themselves to a lot of leniency. But there wasn't any assault capable of causing grievous bodily injury or death. It just didn't happen. No attempted murder.
So if a man wrote in his diary that he planned to kidnap, torture and murder a child and for some reason could only grab and pepper spray a small girl, he would not be charged with attempted murder?
So we reward the incompetent or unlucky criminals for not seeing their plan to conclusion. If the woman had reacted differently to the pepper spray or acquiesced like a coward, we'd be looking at a dead woman.
It's attempted murder.