"So my question is how do you get rid of an attachment that you're not supposed to have that's not healthy?"

The way I ended up doing it was to have the conversation with my therapist. My other choice was to walk away from that particular pain. Both choices were fraught with fear for me, but I threw caution to the wind and trusted to share it with my therapist. We got through it – together. By the way, I went through the feelings of wanting her to be my mother, and hating my sibling (her kid). We talked our way through all this, and got to the other side.

You and your therapist have a long history, and I hope you give her the chance to hear your feelings. I'm pulling for you, Cinnamon_Stick.