Food isn't a cure for bladder infections

I guess in some cases it could be a contributor, but there's no food out there that's going to cure the problem on it's own.
More often than not in the case of recurrent bladder infections, the biggest problem or contributory factor is
lifestyle. Just like us people, a healthy bladder and urinary system is reliant upon taking in plenty of water and urinating frequently. That is, flushing the body of toxins on a frequent basis and NOT holding those toxins and bacteria in the bladder for long periods. Unfortunately, that particular basic principle doesn't work too well with pets and modern lifestyles. Most of us have to work, so that means our dogs are confined indoors all day long without the opportunity to urinate. Aside from then taking in far less water, it also means that - rather than flushing taoxins and bacteria from their bodies every 2-3 hours as they're designed to, they often don't get the opportunity to urinate more often than every 4, 6 even 8 hours. Well, that sort of thing has a cost. Holding the toxins in the body for so long, day in and day out, stresses the other internal organs. And not flushing the requisite amounts of water through the bladder every 2-3 hours means that the bladder doesn't get to rid itself of bacteria, but rather, the bacteria are given ample opportunity to breed... And for some dogs, chronic bladder infections is the result.
I have no idea how long you need to leave your dog during the day.
Does the above apply in your case? If it does, then you really would need to look at the possibilities for an alternative arrangement (dog walkers, day care, etc) so that your girl isn't ever (or at least, is rarely) in the position of holding her bladder for long periods of time.
Another lifestyle thing that impacts the likelihood of bladder infections is the type of food fed. That is, dry food. And that's because it's dehydrating. Feeding a wet food diet (be it canned, homecooked or raw) is far better for urinary health.
Other things that can help a bit with creating unfavourable conditions for bacterial growth in the bladder are apple cider vinegar (the natural type - cloudy, not clear), plain natural yoghurt (probiotics) and cranberry extract. But those are preventative aids, rather than cures. You would still need meds to get the current infection under control - and if clavamox isn't helping, it could be a good idea for your vets to take a culture of the bacteria affecting her and find out which antibiotic the bacteria is sensitive to. Then at least an effective drug can be prescribed.