subscribe to the idea that all horses of "x" breed get "y" angle, whereas others subscribe to the idea that each horse gets their proper "angles" by a careful inspection/review of their conformation (especially where their cannon/fetlock/pastern come together).
I am of the second 'ilk'. I believe all horses & all their hooves(none of us are perfectly symmetrical) are individual & should be treated as such. There are many reasons why a horse may want to be trimmed in a particular way, with regard to angles & balance, that may go against the 'ideals'. So saying, it's important to understand the principles behind the 'rules' & in addition to Ray's pics, I've found e-hoofcare.com to have some good objective descriptions & pics to further explain the concept of hoof balance.
I have a horse who had a highly recommended farrier literally chop straight across the bottom of her foot
Can't comment at all about a specific situation & horse, at least without good pics to give an idea, but general thoughts.... Regardless of how high, low or otherwise the horse may need their heels, I believe it's important to respect the sole plane & not allow the walls to overgrow the sole substantially or to trim the heels(or any wall) so low as to invade live sole. This should also prevent changing 'incorrect' angles so suddenly & drastically as to cause problems. As a rule, horses should have quite short, low heels(compared to what is often seen) & the frog should be level with heel buttresses. It's possible that the farrier in question took the heels down appropriately but didn't address the toes appropriately.
and her heels were basically non-existent.
With respect, you may of course be right, but many people don't realise how low & short a horse's heels should be, or even are(including some farriers). I've heard so many people talk about their horse's lack of heel growth, when the horse has ultra long but crushed forward heels for eg.
been diligently working on my horse to get her heels back "up". We'll make some progress during the warmer months (when she is shod and isn't able to wear down her heel as much), then she drops back down within a month of pulling her shoes
If heels aren't being trimmed but are breaking away naturally when given half a chance, I'd hazard a guess that they want to be that short. Perhaps it's a problem of long toes rather than short heels?? But of course, without more info, only a guess.
If you'd like a critique & opinions of the horse in question, post some hoof & confo pix(see link in my signature below) & more info on management, work, etc. There are a number of experienced people here who can give you more 'food for thought'. Oh & it would be great to see pics fresh after a trim, before shoes & when she's been bare.
I completely trust our current blacksmith, I just want to learn more about hoof angles myself.
Good for you! I think owner education is SO important if we want the best for our horses. I absolutely respect & agree with your want to learn more. But in that regard, respectfully, if you don't understand what's what yourself & you completely trust your current professional, it's blind trust, which I don't think is for the best. Unfortunately there are no shortcuts to doing your own homework, reading & learning as objectively as possible - remember there are likely a range of pros & cons & different theories(with maybe little, maybe good science) behind every idea that is popular. To start you off, the other link in my signature below is a thread with some links to learn more.