[quote=@Ellion]
<Snipped quote by RomanAria>

See, she is bringing them in from outside/ has a stash I can't find. 
[/quote]

Unless you remove the source of her plastic then maybe try some behavioural stuff? Scold her when she eats the plastic and reward her when she eats something less harmful like paper or something to ween her off it. Either that or just feed her loads? [s]Like the flesh of your enemies![/s]

Taking the plastic away probably won't solve it but it'll make it difficult for her, I imagine!