Hiya, Your BO yelled at you for treating your horse for something?? Sounds like a nice, reasonable sort!
Firstly if you want a critique on the hooves, you need to post some good hoof pic(I know that's a bit easier said than done sometimes). They need to be clean for a start. I noticed someone already posted a link for good hoof pics, same link as in my signature below. Some different angles would be helpful, as explained on that page. Is the side to side imbalance in the heels of one foot pictured a very long term thing or only happened recently since the horse has been at the negligent home? Also especially if you're not positive it's her feet that is the prob, whole horses shots, from directly in front, beside & behind may tell us something.
Palpating the hoof & telling what you get is also helpful. Is the sole around the toe at all yielding under strong thumb pressure? If you squeeze the digital cushion - thumb in the 'dent' above heel as far forward as poss, fingers on the frog, how thick/firm is it? If you push your thumb into the back of the frog between the bulbs do you get a big reaction?
There are definitely some issues there, but her feet don't look too terrible really. As you've said the horse was neglected & this is after the first trim in some time, I won't comment on the farriery. The hooves obviously have long, underrun heels, obvious imbalances, but without even seeing before pix, no one can reasonably say he didn't do the best job that was possible at the time with those feet. To 'correct' the issues, I would be getting the horse trimmed little & often - perhaps even fortnightly for a few trims at least - until you get her feet in better form.
What are you feeding her? How much? How often? You said 'grain' but that's not telling much. Generally speaking, free choice grass/grass hay is best and if more than that is necessary for maintenance, grain, due to high starch content & indigestibility is not IMO the best option. There are other healthier alternatives, beet pulp for eg, but if you do decide grain is appropriate in your situation, oats are about the best choice, *relatively* low in starch & unlike other grain, reasonably digestible in the foregut when whole. Other grain should be well processed/cooked before feeding & fed very sparingly & in many small meals daily. If you can't feed little & often, I'd be definitely striving for a healthier alternative. I would also avoid any sweet feed - just like ourselves, eating 'junk food' regularly may stack on the weight, but isn't healthy. But free choice hay/grazing & a good nutritional supp is all most horses need to be healthy.
What sort of environment is the horse in? Is it dry footing? If not, I appreciate it may be difficult/impossible where you are, but I'd move her onto dry footing if at all possible, or at least provide somewhere her feet can dry out daily for some time. Free movement is also important, so don't lock her up at all if you can avoid it.
What did the vet say about the lameness? What did they advise? I'm not clear on that.