I assume she does not understand why she should not. Perhaps she is trying to 'get rid' of all the 'bad stuff'. All I can think of is to try a large cheerful bin, with plastic bag lining, for all the stuff, and see if she can be persuaded to treat it as her 'very special bin for all the nasty dirty things.' You could make it smell nice, using those dustbin deodorisers.
Good luck, whatever you try. Xx