I agree that monitoring feed/nutrition is vital. Similar to diabetes in humans, it is often caused by insuline resistance, so even if the person/horse is healthy & not overweight, the problem doesn't just go away, but needs continued management. I would also check out safergrass.org for info on feeding & nutrition of lami-prone horses. I also agree that if you need a horse that's going to be a reliable ridden prospect I would keep looking. There are no guarrantees. BUT...You'll have to have special shoes for a long time, possibly the rest of her life depending on how bad the founder is. You're right that she's unbreed-able, she can founder again from having a foal. You have to be willing to not ride her or work her for long periods of time if she's sore, because riding her will aggravate it. You have to work with a vet very closely if she starts to get lame so you can stop it before it becomes too late. It's a lot of work, and if you love her, like I said, go for it. But if you need a horse you can ride reliably, etc. I would pass--- once a horse founders there is a high chance they will do so again unless you are diligent in their care.
With careful management & good hoofcare, depending on the reason for her *laminitis*(say cushings, for eg) there is not *necessarily* any reason she can't be bred. I would want to rehab the founder & get her sound before considering it tho. Some horses can indeed become laminitic when in foal, but that doesn't necessarily lead to founder if they are well managed & trimmed. *There is a big difference between lami & founder - one is the metabolic/inflammatory cause, the other is the mechanical effects that *can* come out of it, depending on hoofcare & management.
You do not *need* shoes, special or otherwise, and *if managed effectively*, chances are you won't need to protect her feet with boots long term, except in conditions her feet aren't used to. - eg extra long or rough rides.
You don't *necessarily* need to work closely with a vet, altho I would strongly advise hunting down a *good* one who is experienced in *successful* rehab of founder, to have on call if/when necessary. I would however, suggest working closely with a *good* hoof care practitioner, at least until she is rehabilitated.
I agree with the last sentence, because it has "unless you are diligent in their care". As explained above, horses *can* be susceptible to bouts of laminitis, as it can be caused from insuline resistance or 'cushings' for eg, but they're not more 'susceptible' to actual founder, if the risk of lami is well managed and their feet are *correctly* looked after to prevent mechanical problems.