I'm sorry to hear about your mother's diagnosis.
Nobody can give you any guarantees or promise you that she will be ok, but the outlook for stage ! breast cancer is very good indeed
The severity of a case of breast cancer is categorised into one of four stages.
As others have explained, stage one means that the tumour is small (up to 2 cms) and no lymph nodes are involved. Five year survival rates are almost 100%.
Survival rates for breast cancer have never been higher. I was diagnosed with stage 3 breast cancer almost 7 years ago; following treatment I am well and pretty fit, with no sign of cancer.
Your mother, and you, may find these sites helpful; not only do they have loads of information about breast cancer and professionals of whom you can ask questions, but on th forums you can talk to people who are going or have been through exactly what you're going through. I actually don't know how I would have got through those dark days following diagnosis without online support forums:
My best wishes to your mum - and to you, it's hard to see someone you love go through this
Edit - sorry, I typed the second link wrongly; have now corrected it
This is a very early stage of breast cancer. The cancer hasn't spread beyond the breast at all. So you have a number of good treatments to choose from. The eight-year survival rate for women with stage I breast cancer is about 90%.
Stage I: Your cancer is less than 1 inch across (2 centimeters) or about the size of a quarter. The cancer is only in the breast and has not spread to lymph nodes or other parts of your body.