Afraid recurring abscesses are either a sign of ill health of the hoof generally, or that the treatment/management is not great. Would need more specifics & pics to tell you more than general stuff though.
^^^Ditto. The only horses I am familiar with that had recurring abscesses, literally one on top of the other, had immune issues and health issues.
The health issues were Insulin Resistance and Cushings. Eleven is plenty old enough for either.
You could consider bloodwork.
Also, you don't mention what the horse is eating. IMHO if she's eating any sort of grain and soy products
(including ration balncers) I would get her off them to reduce the starch load as much as possible.
If she's eating alfalfa, it might be best to get her off that or at least reduce it down and mix it with a quality grass hay.
If, on the off-chance, you are feeding BOSS, get her off that five minutes ago. BOSS is high in iron and Omega-6 but no Omega-3's. Omega-6 is known to exacerbate inflammation of any sort.
These are just some diet things that can be done to help but they don't always.
During the last six months of my friend's IR/Cushings horse, nothing she did would stop him from abscessing and abscesses had started in more than one hoof. The diseases had suddenly drug his immune system down so low that he also ended up with pneumonia.
I'm not saying this is the case with your horse but this is a first-hand experience of what MIGHT happen when the root-cause of recurring abscesses can't be discovered and brought under control.