I am so sorry to hear about your sister. The supplement that you are referring to is an extract made from the oleander plant and you can get that at http://www.sutherlandiaopc.com. Make sure you get the supplement with 100% oleander, as it may be more effective. Also, the oleander extract does cross the blood brain barrier.
Besides taking the oleander extract, I would suggest that she also take colloidal silver and curcumin. Both have strong anti-cancer properties,and curcumin has valuable anti-inflammatory qualities.
And actually, I would really not stop here. With the stage of your sister's cancer, you should implement every compatible alternative means possible and these alternatives can be found in A Natural Anti-Cancer Protocol. This protocol includes other important cancer fighting and immune strengthening supplements, together with diet and lifestyle recommendations. Something else that I would urge you to do is the Budwig Diet portion of the protocol, but honestly, at this point, I would urge her to follow it in its entirety.
Lastly, I would like to invite you and your sister to join our yahoo natural healing group, Oleandersoup. Here, you will find others using oleander and the protocol to heal naturally from cancer.