Is she having a history of bone or joint pain previously as well.
Just hugging someone should not cause any bony injury unless the bones are very weak.
Most probably, it may be due to some muscular strain around chest region.
Next Steps
She may start with analgesic and muscle relaxant tablet for pain relief.. If pain is severe, better to get one X ray done to know the bony condition..
Health Tips
Avoid heavy work, avoid forward bending..