Can Thick Phlegm Production After Tonsillectomy Lead To Pneumonia?

My daughter had her tonsils taken out and tubes put in her ears 4 days ago. She had been on an antibiotic for upper respiratory about 5 days prior to her surgery and she still had a cough and mucus production the day of the surgery. She has nasty rhonchi! It is a thick yellow color. I knew to expect extra mucus production with the surgery but this is so much its causing her to vomit. Breathing treatments help a little but should I be worried she may get pneumonia? I think she may need a antibiotic and maybe a steroid. Any suggestions?