My 12 yr old daughter is suffering w/sinus tract inf. & w/ asthma. She is currently takin nebulizer treatments & prednisone. Isn't working?

May need antibiotics. Take her to your doctor. If she is not getting better, she may have an infection that is not being treated (such as bronchitis or pneumonia). She would need to be examined and possibly get a chest xray. If her asthma and her breathing is worsening despite nebulizer and steroids, you will need to seek medical care immediately as she may need more intensive asthma management.
Document and treat. With the above hx, a sinusitis not responding to rx, which i presume from your history, can cause this. An x-ray/ct to document sinusitis would lead a doc to change antibiotics if there is a lack of response, or look for other causes (severe allergies, gastroesophageal reflux, airway irritant exposure, pertussis, etc.). Pulmonary functions to ascertain how much asthma is contributing can be helpful.