My 7 yr old fell last weekend and is now complaining of her chest hurting? could this be a coincidence or could it be relavant to the fall?

Possibly: Your child probably has contusion (sprain/bruising) from the fall with i wound recommend going to pediatrician for for some xrays.

Evaluation : Please see your physician or urgent care. The rib cage may be bruised and applying local heat and giving Ibuprofen is suggested. If there is a fracture of the ribs, there will often be associated pain with breathing in.