Don't know. Anxiety or any other issue?

From past couple pf months, My sister is facing issues like racing heartbeat, pain in left area muscles, neck muscle stretch sometimes, upper abdomen muscles pain, panicking, shortness of breathe/ irregular breathing sometimes, talked to a cardiologist also he checked ECG and ECHO report came normal nothing abnormalities and said it's anxiety. Been on benzodiazepines composition also but it got her relaxed for sometime only. She feels weak also and lost weight. Feel heaviness in chest area also. Yes it's true she panicks alot in small things, bad thoughts when rush through her mind it got her into overthinking and racing heartbeat. What is it please Guide..? After some activity also she faces as if heart is beating fast.. from past 3-4 months she is facing. No medical history. Please guide is it anxiety or any other issue?