Persistent coughing & tastebud changes after radiation.

Hi. My mom had 6 weeks of Partial-Breast Irradiation(PBI) after being diagnosed with Stage II Breast Cancer earlier this year.

She had a lumpectomy with a lymphovenous bypass (to prevent lymphedema) and then 6 weeks of PBI.

3 weeks after the Radiation was over she started having a persistent cough that has led to coughing spasms that has caused her to vomit twice, feeling drained of energy (fatigue), and her taste for certain foods have changed. She feels as if only fruit taste good now. Some days she feels okay enough to work, go for a walk, and get things done (despite the cough).. but other days she feels so weak. At first when the coughing started we thought perhaps she caught the coronavirus but has tested negative twice, than we thought it was allergy related, but after multiple allergy tests they found she wasn't allergic to anything that would be causing the persistent cough. She also had scans done of her lungs but they found no issues (pneumonia, etc.) and she has had no breathing-related issues. She has other tests scheduled to find out what's going on but they aren't until later this month & July.

It's been two months now since the last radiation treatment yet the coughing, fatigue, and tastebud changes have still continued. Is it normal for radiation to cause a persistent cough & tastebud changes? I know fatigue is common but has anyone else had a persistent cough or noticed tastebud changes?

She also has tried all the known coughing herbs/remedies (cough drops, cough syrup, different vitamins/herbs) but none seem to really help.