Taking over responsibilities for Mother. What am I doing wrong?

have taken over responsibility for bills, medicare etc. but am not always there when mother opens mail. she opens it in different locations. stuffs it into folds of newspapers or magazines (which all go to recycling at some point), leaves it lying around for caregivers to read, loses it, stuffs into pockets, left out on the porch under seat cushions.Have tried to get her to put into one place. she gets angry that the point is being belabored and that I am not clear and am in incomprehensible. All I ask is that it be put into one folder marked for me to go over when I am there. How can I make it any clearer? What am I doing wrong.