Does My Niece Have Asthma Or Food Related Allergies ? How Can These Conditions Be Treated In Children ?

Hi,my brothers daughter 11years old.she has breathing problem.the breathing problem occur in between 5-6pm.we went to doctor he did her chest x-ray and Eco there is no problem in test.doctor did the physical exam but every thing is ok doctor said.my mom has asthma problem and I have food allergys.her breathing problem was not befor it s suddenly started.but that day she ate lots of peanuts.we have no family tension.please kindly help me beacuse that time daily(5-6 pm) she has very difficult to take the breath.this condition 1 time breathing is in normal weather but weather is changing like rainy she getting 3-4 breathing problem.please kindly guide me what has.(her weight is around 30kg.and height is 4feet 2 inches and no caugh no cold no noise is coming from chest)thang.