I agree with Lee. There comes a time when, even if it hurts to no end, you have to cut the ties that bind. You are being undervalued and disrespected, and it's the kind of thing that could wreak havoc on a person's psyche. That's almost like saying your possessions, needs, wants, desire, space, etc., isn't as valuable as the other sister, and that would be a gross misstatement.
As a grown woman, you shouldn't HAVE to lock your things away!! She should have more respect for you and your other sister. As a grown woman, you shouldn't be made to feel inadequate or as if your thoughts and feelings have no value. I heard something once that I didn't get then, but I completely understand now. When a mother was asked which one of her children were her favorite, she replied 'Whichever one needs me the most at the time.' We don't play favorites with our children, rather than make them all feel as if our world would cease to exist if any of them were no longer a part of it.
Have you ever told her how if affects you and your sister to be treated this way? If not, I would. If you haven't, I'd reaffirm my vote for putting a little distance between yourself and them.
XoXoXo
