My Wife Has Been Experiencing Pain In Between Her Shoulder

My wife has been experiencing pain in between her shoulder blades, specifically when she takes a deep breath. This has been going on since she awoke this morning. Hasn't gotten worse through out the day maybe a little better; the pain is constant (2) but increases significantly when she takes a deep breath (6/7). Not sore to touch. She tried to walk with a friend this afternoon and had to stop because she couldn't take deep breaths.