This may or may not be a joke.

However, you must adress the underlying reason for an illness or it will keep producing disease and the question here is why it appeared firstly in her breast, a motherly\female organ.
Cancer is considered a disease of desperation and powerlessness and possibly this woman does not feel appreciated in her feminity and motherhood.

She is very frightened right now and the pronostic appeared very dark at first - and I was not going to post - but there is now light around it. Wether she can use the impulseto pry herself up is up to her. I am getting her as paralysed while she must be proactive.
Many people choose to die on an unconscious level or because they cannot resolve the inner conflict.

A total change of diet is also important in such cases: no meat, processed especially, no white sugar etc. The person must be willing to do this. Some prefer the grave and a pitza.
A surprising amount of people do.

The fact that she is now coming down with the disease could also be a healing sequence, according to some school.
If you had been a drain on your parents and you finally moved away, her body is reacting but the “healing” crisis is often what kills people. This sequence of events happens a lot but is not ackowledged by traditional medicine.

I really really do not want an answer from you but posted here in case it comes in helpful to someone else or even your mother. Maybe she should read this and into this.