Thanks so much. You guys both made so much sense!
Lynette, I'm 25, and yes, it hurts a lot to think that I may have to "be my own parent." I'm so glad that you can relate to what I'm talking about here, though... thinking back, it becomes clear now that you're right. She's always had a "project," whether it was my first bout with depression when I was 12, trying to force me to continue figure skating when I was 16 and wanted desperately to live a "normal teenage" life, or using my wedding as a distractor from my sister's habits. The only way I do get maternal attention from her is to have something to "fix." And I don't want that.
I'm also glad that you said that this feeling can hurt like a loss. I've been grieving a lot over the past few years. I've experienced what I can only compare to the feeling of the death of each of these people many times over, and it actually at least feels good to have someone else compare it that way. I've always felt like it made me a bit of a nut that I thought about it that way.
Chino, thanks for your response as well. You have an interesting point too about her not knowing how else to communicate with me. I guess I could try emailling her.