My mares hooves are as soft and brittle as can be and she often comes up lame from it. Is their anything that's healthy for her that I can feed to help strengthen the feet? Something CHEAP!
Comes up lame from what exactly? If she has soft, thin soles, could be diet/nutrition, &/or environment, &/or the way they're managed. I hope if she has thin/soft soles, you pad/boot her feet for work? If not I'd definitely be doing that. Certainly as diet/nutrition are huge factors in horse & hoof health, that's the first thing I'd look at. Re supps, you tend to get what you pay for, so if the outlay is cheap, it's quite possible that it's less economical, or a complete waste of time compared to a good, more expensive product.
Also, is their anything I can feed her to help the days she is in heat? I have heard of raspberry leaves
I'd go the raspberry.
they are super nervous or scared? Is their anything I can put in their daily feed for a while
Horse's diets are very often deficient in magnesium, which among other effects, will cause horses to be more nervy. Stress, whether physical or mental, high carb diets and too much calcium are some of the things that further deplete the body's magnesium. Therefore that would be what I'd be giving a new, stressy horse. Quite possibly not just 'for a while' though. Depending on diet, nutrition, lifestyle, etc, it's probably something most horses need extra of as a rule.