My husband and I have had the toilet paper roll discussion (he leaves it empty) and you might point out to your Mom that there is NO DIFFERENCE in whether you change it for the "next" person (who could be you!) or get it and put it on the roll when you need it next. At some point everyone is going to have similar odds of being last/first.

She's "crazy" - you know that, don't let it hurt you anymore than you have to. I had to go to the bathroom after dinner once when it was my turn to do the dishes and my stepmother swore I was trying to get out of doing the dishes! She angrily did them and held it over my head. Excuse me, but I can't stay in the bathroom all night? A minute or two tops? The dishes can't wait?

I'm so sorry Inny that you have to go through all that. One suggestion, don't EVER not buy her a Christmas present; I did that once when I was in college, the present I found I went to pick up and it wasn't what I thought and wasn't appropriate and I didn't have time to find another. I still cry about that Christmas day and her, "Nothing!" in tragic tones.