My sister 59 has stage 4 vulva cancer and is now terminal, how far up the trunk of her body will the cancer spread.

Vulvar cancer: If a woman is dying from vulvar cancer, she will likely die from effects of distant spread (mets) before the tumor spreads locally from the vulva on to the abdomen.

Palliative care: I am sorry to hear about your sister's serious illness. If she is stage IV and terminal, it is more important to worry about symptom management than the specifics of how her disease is progressing--there are no more stages of her cancer. I hope you are in contact with palliative care doctors who are managing her pain (ask about neuropathic pain medications), bowel movements, mood, insomnia, etc.