Dry hooves & environments aren't a problem for horses. That is the natural state. However, when hooves look overdry - eg. They're shelly or peeling, the walls have lost their outer coating & are full of 'microcracks' or such, this indicates problems. I believe it's generally due to diet & nutrition, or too wet environments. Can be other reasons, such as chronically unhealthy feet with compromised circulation, infection, laminitis, etc.
Chipping generally means the hooves could do with more frequent trimming &/or keeping a 'mustang roll' or bevel to the outer wall. Vertical cracks can be due to just excess wall length/insufficient trimming, can be from hoof imbalance, infection or abscess or such blowing a hole in the wall.
Yes, hooves do absorb moisture in wet environments & as with our own skin if we soak for too long, this makes them softer & weaker. This also leads to them being compromised enough to be more prone to infection such as seedy toe & thrush. But it's the inner wall & sole that hold & can absorb moisture. The outer(healthy) wall has an impermeable layer over the top.
So... I would start by assessing her diet & ensuring the grass isn't too sugary/rich, or just too much of it if she's overweight. I'd also provide a good nutritional supp or ration balancer to provide her the nutrition she needs. I'd also include some fresh ground flax/linseed or such, for the omega 3s. FeedXL.com is a great program/service IMO for diet/nutrition information & balancing.
I would ensure she has her feet well & frequently enough trimmed and if at all possible keep her in a mostly dry environment. Any hoof wall infections need to be treated, as if the cracks are infected, even with adequate trimming, it can eat away at healthy horn quicker than it can grow.
And I wouldn't be putting any topical goop on the horse's hooves. This is generally at best useless, aside from cosmetic value, but it can also make matters worse. Here's a link to one study done on hoof 'dressings'; The Horse | Hoof Dressings: What Studies Show
If you would like any specific advice or opinions on your horse's hooves, pics(see link in signature) & more info will be helpful.