Get her name and file a report. DON'T LET HER GET AWAY WITH IT. Everything she does, screaming, putting crap on your doorstep, is harassment. I know it seems like nothing, but it could escalate, and its always better if you have these things documented from the beginning. When you see her, ignore her, if she starts screaming walk away. Confronting her will probably not solve anything and she will just become more irate.

I have a similar CRAZY neighbor. I never went to the police because my boyfriend told her if she ever approaches me, I will report her, and luckly she backed off after that.

I am sorry you have to deal with someone like that.