Well, I am going to try to give my un-biased opinion here because your sister sounds exactly like my sister with the crisis and drama etc, so much so that it's really kind of scary! So, I will tell you how we (my family members) handles this with her (my sister). We just let her talk and acknowledge hearing it but let it go in one ear and out the other. Basically that is really all you can do IF you don't want to cut ties completely. With my sister, if anyone tells her of someone we know whether it be another member in the family or a friend or relative that is going through something *cancer, surgery, painful testing, it doesn't matter what really*, she will SWEAR that they are going to be fine, that she went through or has the same exact thing. She is a Hypochondriac!! She has everything in the world wrong with her and is on every pill imaginable! Oh I could give you stories after stories about the things this woman has done and it would seriously flip your lid! I laugh about it now, because there is really nothing else you can do! I know it's sad that she has issues, but when you live with someone like this all of your life, there is a point at one time or another that you just have to get over it, brush it off your shoulders, let it be the way it is!
I understand what you are going through with all of this. Something VERY similar happened in my family when my mother passed away. I won't go into any more details on this thread, but my advice would be to go at least for now, listen to her, and if it just doesn't settle right with you, maybe talk to her counselor and ask them what they suggest she is going through or how you should handle her "situations"
Sorry if I sounded so blunt and "not caring" in this thread, but you have to really live in this situation to really understand what someone is going through.
Some people are more emotionally fragile than others and, therefore, have difficulties coping with disappointments and loss... regardless if they're first, middle, youngest, okay or not okay about being adopted. So, why can't "compassion" be spared for the troubled middle child? Are her needs that great? Is her behavior that problematic?
What may appear on the surface as an attention grabbing "ploy" may very well be a desperate cry for help... this is something that should not; nor can not be ignored.
Textbook, let me guess. You're the eldest.
You were adopted as an infant, she was adopted as a near toddler. Worlds apart.
When you say "textbook middle child", and then go on to say in complete contradiction that your mother has balanced your lives equally . . .what a complete contraction that is?
My guess is your sister is a combination of being adopted later in childhood, being the middle child, and the genetics from her parents that would create a situation where a 9 month old child is up for adoption.
If you've given up on her, do. Just don't think it's because you have greater character than she does that you have turned out better.