TBs are not known for being IR at baseline but they can develop IR (which could show as a cresty neck and fat deposits) as an offshoot of being PPID (commonly known as Cushings). If you're mare were mine I'd be having bloodwork pulled to get her ACTH level checked - Bonnie outlined the details on this in your welcome letter. You can add glucose and insulin to that as well to confirm if she is/isn't IR at this point. The fact that she's now had 3 cases of laminitis is very suspicious for it being related to PPID, especially if all 3 instances have occurred in the fall.
Feeding a horse apples could possibly cause laminitis in a horse with IR, but again, that's not very common in TBs. Also, it was in the past and you can't change the past so you need to focus on getting her better.
If you can get a case history started and photos/xrays posted on the Case History group (details on all this are in the welcome letter) we'll be able to help you assess if her current trim is correct or if it needs to be corrected to help her heal. If the shoe was put on a hoof that wasn't trimmed as it should be it could be causing more issues than it's helping. For this reason we prefer to leave horses that have had laminitis barefoot and keep them booted for comfort as it enables more frequent trims to be done.
Even with shoes on you can use styrofoam taped to the bottom of your mares feet to help her feel better, it just may not have the same effect as if she had no shoes on.
IF the laminitis is metabolic in origin Bute will not help so it's good that she's off of it, but the Meloxicam is just another NSAID and also will not help her. What will help is finding out what's causing the laminitis, removing the trigger and getting her trim and diet in order.