He checked her over throughly and said her hoofs were great.
Then did he give an explanation of why she's having difficulty, if everything's so perfect? Why is he grinding out the shoe & using foam if there's nothing wrong?? Sorry, but without more info, your report doesn't give me any reason to believe what your farrier seems to.
grind out alittle of the shoe to on the inside so it won't press against the sole at all.
It is very possible, by the sound of it(without more info & pix only educated guess tho), that she does indeed need protection for her feet, not just shoes. But forcing the walls to support the entire horse, rather than spreading the load & allowing the soles to also play a part in support as they are meant to, is generally problematic. Of course there are exceptions; if the horse were foundered or otherwise needed the toe sole to be relieved temporarily, or if the other guy did indeed thin the sole there...
Now it seems that I just need to put her on a diet. Any help out there???
Sorry again to sound negative, but agree with dee - your diet plan for her is not a good one!
Horses are best not locked up at all, so avoid this if possible & try to find an alternative. Of course I appreciate it is sometimes the only option tho. Googling 'paddock paradise' will give you some better ideas that you may be able to implement. If you do need to lock her up part time to keep her from rich grass, it's best to keep her off the grass during the day & let her out at night, as sunlight & photosynthesis is what produces the sugars in grass, so it's lower at night. Also if she's kept locked up, you need to take her out for lots of exercise.
Horses have evolved to be 'trickle feeders', eating little & often & it's not healthy for them to go hungry for many hrs. This causes stomach ulcers, colic, etc. Therefore I would leave her with free choice hay, BUT if you put it in a small holed or doubled hay net, or some other form of 'slow feeder', she'll have to work to get little bits & won't be able to gorge on it. Therefore she'll eat less, but won't be left to go hungry. If she doesn't lose weight with this, then you can progress to soaking her hay, to leach out more of the sugars. Regardless of their size, it is not healthy for a horse to drop or gain a lot of weight suddenly either. It is best done gradually.
What is the other 'feed' she's getting? I wouldn't advise giving her any, aside from a vit & min supp to ensure she gets balanced nutrition. If you are going to keep feeding her, ensure it's a very low-cal feed with no grains or sugar(molasses) in it.
safergrass.org feedxl.com and many other good sites will give you more info on healthy feeding practices. barehoofcare.com (also explains when shoes may be beneficial or not) is another good site to learn about hoof care. Do your homework asap & you will learn what is required for good management, health & feeding of a horse.