Thanks for your question on Health Care Magic.
I can understand your concern.
No, this is not related to
costochondritis.
Costochondritis can cause
chest pain. It can not cause leg pain.
Your daughter is mostly having
sciatica (pain of
sciatic nerve). Sciatic nerve is originating from lower back and runs downwards in the leg.
Lower spinal compression can cause sciatica.
So in your daughter's case possibility of sciatica is more because her pain is starting from back and going lower down in the leg.
So better to consult orthopedic doctor and get done clinical examination,
x ray of lumber spine and MRI of spine if needed.
So better to first diagnose and then start appropriate treatment. Costochondritis is not a cause for this.
Hope I have solved your query. I will be happy to help you further. Wishing good health to your daughter. Thanks.