I used to keep a large bottle of OtoCetic around for my old dog with chronic ear infections. 3 washings the first day, then 2 then 1, then 2-3 times a week.
You might want to ask the vet that found the bacteria what type of bacteria she's got (basically gram-negative or gram-positive) and get drops to kill it. Chronic bacteria infections can lead to worse things including precancerous growths, burst ear drums and deafness.
White vinegar and water mix is also good, just don't use it on broken skin. It'll make things worse.
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