I just want to add to Loosie's post that many times coming out of shoes is when a hoof is prone to abscessing as the improved circulation lets the foot start to correct problems and clean up the cellular debris. Picking out the feet is good for preventing thrush and letting you assess the condition of the hoof visibly, it won't do squat to prevent an abscess unless you are picking out big rocks (which you generally don't find in bare hooves, anyways, more so in shod feet as the shoe creates a "cup" that holds in dirt and rocks ).
The best way to get rid of abscess issues is to keep the shoes off, do some epsom salt soaks to promote the healing of existing lesions and work at conditioning your horse's feet. Keep off large, scattered stones for a while and either use boots to protect the feet (boots still allow a more natural function than metal shoes) or keep your horse on softer terrain for a while until this super sensitive period is over. By conditioning, I don't mean moisturizer, either, but exercise on the right types of terrain. Your horse WILL get through the abscessing stage and have better feet for it.
If it's truely persistent, then I would look at metabolic issues, Too much sugar in the diet,mal nourishment or an insulin resistant horse can be prone to sores in the their extremities, but your vet would have to diaganose the insulin resistance. A malnourished horse probably isn't your situation, however excess sugar could be.
Also, if you are in a really water logged area right now, the hooves will be softer and easier to bruise on rocks, and bruises can lead to abscesses, so I'd suggest boots for rides until it dries out a little, and she can toughen up more.Its still healthier than metal shoes.