If you intend on healing, I would sugest asking her first. If that isn't possible, try to ask her higher-self (this is only a sugestion, it depends on your path if you would ask her or not).
Do you know what kind of cancer it is? (Like there could be an underlining cause of why there is cancer)
Most of the time, people who 'die from cancer' die from things such as infection from the cancer interupting the bodys systems.
So, I would sugest cleaning and balancing the Chakra's, then attacking underlining infections, then useing energy to tell her energy to clear the meridians and damaged chakra's. When her energy system is ballanced, focus on repairing the cells that are malfunctioning. And clear, clean or destroy the underlining problem (such as toxins, or virus). Draw energy in whatever manner you prefer, and use visualisation, and project the charged energy to the person. If it is distant healing, one effective visualisation is making a ball of energy, and visualising the person inside the ball of energy, then it is easy to send the desired energy to the person).
If you need any help, let me know - I would be willing to do an online ritual with you, as long as you have atleast asked the person's higher self if it ok to heal.