Mother diagnosed with lung cancer WATCH & WAIT

Previously my mother was diasgnosed with bowel cancer in 2018. She had a resection. Needed no further treatment. Her year CT was last November. They found something on her lung. She had a PET scan. A week later a biopsy. Results came back as lung cancer. We were devastated. All her scan are clear. It is not secondary Thank God. Last week they rang to say the biopsy results showed it is a small, very slow growing cancer. Possibly has been there for a while. The best news we could possibly have. However yhey are undecided on treatment. Risks of surgery, side effects of radiotherapy or to ' watch & wait'. The latter terrifies me as I just want it gone asap. We have an appointment in 2 days to discuss all options. My mother is a young 72. Fit and well and completely symptom free. They said it would never have been found if she hadnt had bowel cancer. Has anyone had experience of ' watch & wait'? My anxiety is through the roof, feeling soo lucky but yet terrified x

I forgot to say.. they saw it on her first bowel cancer scan 14 months ago and thought it was scarring. As it had slightly grown that is why they decided to do the PET scan.