Does your sibling openly agree regarding the cause of her issues, and did the same things affect you? If so, perhaps consider the good idea another poster had of giving her lessons as a gift, but give yourself something you need, too. Explain to her that you would like to take steps to make you both more whole and healthy; you are trying to repair some of the damages to you both, because you CAN. Explain that you know how fractured a person can be from neglect, and how empowering it can be to mitigate some of those issues. Assure that she will be so much more confident and happy, and that its nothing to be ashamed of. Your parents probably had their own issues and never intended for this to happen to her- if so, maybe tell her that it could help lessen their guilt and go towards healing the whole family if shes brave enough to try. Tell her how you are inspired by her bravery, when youre finding the gift you're going to give yourself.