So this is pain in just the right side around the chest / breast/ shoulder area?
Do you have any pain in the abdominal area?
Has she seen a Breast surgeon?
Usually the pain that you describe is actually Referred pain from just underneath the diaphragm - so the nerve in that area of the diaphragm can cause all the pain that she is experiencing.
So, what I would suggest is a MRI of this area since the ultrasound things such as an ultrasound, and gastroscopy was normal.
IF the MRI is normal - then I would THEN next check with a Laparoscopy - which is a camera that looks directly at the diaphragm with a camera - as she might have an infection going on in this area, or she might have something going on with her gallbladder which is a fairly common problem to cause this too.
Also, the MRI of the Breast might help too - as there could be something going on with an interaction between the breast tissue and then with the muscles on the chest wall below / behind the breast - and a MRI can pick this up.
If you have more questions, please ask - I am here to help you
I wish her well
I see you have not returned.
Have a good day