How horrible for your little labradoodle, I can understand your concern. The symptoms you describe are quite broad and could be due to several underlying causes. Itchy skin, if localised to one area such as the nose can be due to allergies or even auto-immune disease. The fact that she is also congested is a little concerning as this may be indicating a respiratory disease or if the discharge is from one nostril, it may be a symptom of a foreign body in her upper airways or nose. It sounds like you have tried different treatments and if cortisone tablets and antibiotics were ineffective then I would seek a second opinion.
Chronic problems such as this may require further diagnostic testing or medication trials before a diagnosis is confirmed. Your little pooch certainly cannot continue like this so it’s time to have this problem thoroughly investigated. I wish you the best of luck and hope your furkid is feeling better very soon.