You do not need to blame yourself for your sister being unlucky. People can be blessed or cursed from birth depending on their natal chart. A person's natal chart is the positions of the planets at the exact moment they were born and is a map of their soul. A natal chart shows someone's past, future, weakest/strongest chakras, likes, dislikes, and everything else about that person. If your sister has a lot of karma (programming, trauma, and other dross) from a past life, that can cause misfortune in this life.
Karma is NOT some divine retribution for bad behavior in a past life. Karma is just a term for dross brought into this life from previous lifetimes. For example, if someone was worked to death in a previous life, they may be born crippled this life because the trauma was so massive that they never wanted to be worked to death again. By being born crippled the person cannot be worked to death.
Azazel's Astrology for Satanists
www.angelfire.com/empire/serpentis666/FURCAS.html
You can help your sister by encouraging her to do yoga. Yoga blasts the body with high-vibration energy and clears out spiritual dross. You can do yoga with her or tell her it will improve her health if you need to so she will do it. Yoga does improve health, increase energy, banish depression, and bring many other benefits in addition to the spiritual benefits.
You can clean your sister's aura and build an aura of protection around her like you would yourself. If someone does not clean their aura, negative energy from their environment will stick to them and attract bad luck, disease, and other unfortunate things. A strong aura of protection reflects negative energy and prevents accidents, physical or psychic attack, and other misfortune. We are in a spiritual war here and you should be cleaning your aura and building an strong aura of protection everyday, multiple times daily is better. Satanists are cursed as a collective and neglecting to build an aura of protection is asking for disaster. You should wait at least 30 minuted after building your aura of protection before protecting your sister so the energies do not interfere.
Aura Cleaning/Aura of Protection
http://josministries.prophpbb.com/topic16800.html