Many factors can affect what will happen in the days to come. Many of these factors will affect both your mother's physical and emotional well being. It sounds like you
are providing support to your mother as quickly as possible.
Up until now, the chemotherapy and radiation were intended to stop or slow the growth of any cancer cells throughout her body, now that these treatments will no longer be given; the cancer will spread and will affect not only her lungs but other major organs within her body.
You mentioned that your mother has a diagnosis of terminal cancer. A terminal diagnosis is typically defined as a condition where the life expectancy is estimated to be for 6 months or less.
Based on your mother's diagnosis, I am hopeful that you, your mother and physician had an opportunity to discuss end of life choices/issues prior to the decision to stop treatment.
If not, I would recommend trying to have this discussion as soon as possible. Once you have a sense of what your mother is thinking and feeling about her condition, you can better prepare her and yourself for the days to come.
I would recommend you request a hospice evaluation from her physician, so that you and your mother could have additional resources available to help with a variety of concerns, such as her day to day comfort, pain control, spiritual support,possible 24 hour caregiver assistance, and community resources.
Caring .com has a section within the web site titled "˜Hospice Resources' which offers helpful information about hospice care, locations and financial information.
Another resource you may find helpful is hospice care giving.