What Causes Chest Pain While Exercising?

Hello, my 15 yr old daughter is active, fit and well. However she has begun to have pains in her heart area for the past 12 wks or so, that seem to be coming more frequently - once a week ish, when she is doing exercise. A gp friend suggested it could be costochondritis and use ibrupofen but to get her checked out anyway. A locum saw her today and has asked her to try a blue inhaler, 2 puffs, before exercise begins ? Dont quite understand this. She does not have breathing difficulties before, during, or after excercise or when the pain occurs. Thought inhalers were to widen the air way when breathing was becoming a difficulty? Non of this fits my daughters symptoms. The gp said he wanted to try this to see if it had any affect and to come back in 2 wks. Said he didnt think it was costochondritis as there was no localised tenderness in the area. What could this be?