I'm sorry for your mother!

She is having an advanced breast cancer, cancer that has spread beyond the breast and nearby lymph, to other organs.
Bones are usually first place for breast cancer to spread.
With stage 4 breast cancer, it is typically impossible to kill all of the existing cancer cells.
However, breast cancer treatments can shrink existing tumors or slow the growth of cancer cells.
So, it'll provide symptom relief and extending the life expectancy of patient.
One recent clinical study data shows that patients receiving Femara have median overall survival of 35 months.
Only 20% of breast cancer patients with advanced stage of disease, will be still alive five years after diagnosis.
Acctually, the "average" life expectancy from diagnosis of bone metastases is 2 years.

Thank you so much for posting an answer. I will share the info with my family and this will give them some parameters with regard to spending quality time with mom.

God Bless you.

God bless you and your family!