My daughter had tubes at 9 months also, and has still had an ear infection. From what I understand, they still get infected, but the bacteria can drain out and it doesn't fester in the ear canal.
Are you careful not to get bathwater or swimming pool water in her ears? Do they have you use drops at the onset of the infection, like Ciprodex?
We started looking for alternatives to treating the causes why my daughter was getting so sick. We started washing her hands before eating at home and when she gets home from daycare or an outing. We started giving her a 1/2 Flintstone gummy vitamin each day. She gets 1 scoop of Rhino Powder acidophilous for babies each day in her yogurt to help keep the good bacteria in her system. And we started seeing a chiropractor who specializes in babies.
She went from going on antibiotics every 14 days to 45 days. I hope that you will be able to find something to help your little girl. I know how frustrating it is.
Also, she may have a food allergy, such as milk. You might try rice milk for two weeks and see if her condition improves. Cow's milk actually adds to mucus production.
Good luck!