As far as I know, you can’t “press charges” here as they do in the US, so if the police / prosecutors have charged her with something, then they must have some evidence. Throwing things from high floors is taken pretty seriously in HK, no matter whether the window overlooks trees or the street. Your friend could be in trouble. If she has a lawyer, the she should follow his/her advice. The lawyer is not there to answer “what if” questions, so if the case has been heard, it’s just a matter of waiting for the verdict or next court date.
If the husband has changed his story, then he either lied in his initial statement to the police, or he is perjuring himself by lying to the court. Neither is a good idea - wasting police time and perjury can both land him in trouble.
I agree with newhkpr - everyone sounds awful in this story