So sorry your sister showed so little sympathy. That really hurts.
You know we know how you feel and cry and grieve with you. Having lost Potion, Melody and Bandit in about 10 years I can appreciate how hard it is. The only advice I can give is give it time and let the sweet memories help you through. Be sure to tell your doctor about her passing. You need to be in the best possible mental position to fight the cancer.
Sending more hugs.