Doing a phd for the past 10 years, is that not slightly worrying.....?????? Surely if she can't even finish her own, she shouldnt be "supervising". Unless of course she needs studies that take over 10 years to carry out.
It's obviously a big problem, you need to talk to the "mean" supervisor and tell her that you don't appreciate being treated like that. If she's not understanding, threaten her by burning her work, if its taken 10 years to do, she will be worried!