I think perhaps that I would look at yourself and your sister as two victims of a very disordered and manipulative Mother. Your Mother has spent your entire life trying to split what you and your sister have, out of pure jealousy. Yes your sister has made some awful choices, however, given her choices were steered by the emotional abuse of your Mother, I have to think that your sister would have chosen differently had she had a loving and supportive Mother.
Your achievements are no reflection on your parents, you have achieved what you have in spite of the emotional abuse and benign neglect of your Mother. Your Mother’s narcissism saw her bragging about you, purely to take praise for your successes.She used your achievements to belittle your sister and beat her into her role as her beloved, broken child, who in her absence had utterly failed to thrive without her Mother there to take care of her. She needs your sister to remain broken and weak, needing her, to inflate her own sense of importance.
You fought to make your Mother proud, as you desperately wanted her approval and love. Your sister felt she could do nothing at all to even begin to be as successful as you.
I am in no means dismissing your abandonment or the emotional abuse you have suffered (which has clearly had a lifelong impact on you), however your Mothers savage cut to your umbilical cord has allowed you many more freedoms than your sister. You have been very much allowed to spread your wings and soar. Your sister has been entrenched with your Mother constantly belittling her and making her feel broken and inadequate. Your Mother hasn’t allowed your sister to even grow into a fully functioning adult, who is capable of standing on her own two feet.
I wouldn’t be too hard on your sister. She has a lot of healing to do and hopefully a lot of growing too. She will need your support and encouragement to learn that she doesn’t ‘need’ your Mother and that she is a capable, strong and intelligent woman.