That is an interesting dream, Candy, thanks for sharing it. I've read that since it's our dream we're dreaming, we're all the characters in it.

If yours were my dream, I'd imagine my "sister" was a reflection of me and/or my "mother" is a combination of me (over here) and my sister (over there), a kind of synthesis; cutter and worthy of "defense" or protection against me and my insistance about therapy. It looks like I (as dreamer) feel about cutting (for me) as my mother feels about therapy.

I'd try to think of cutting the way you think of therapy for your mother's depression? Or give yourself the same break for cutting that you give yourself for depression? Play with the "pieces" that way; they're all your pieces? See what they have to say to you that gives you new insight/help.

I hope the ugly feelings go away soon though or can be replaced with good thoughts/ideas on how to approach your struggles.