having buried her nose so far into the books that she effortlessly and immediately fixes Harry’s glasses upon meeting him

This happens only in the movie. In the book, she just mentions that she had "tried some simple spells", and that they had worked for her, but doesn't list what spells they were or demonstrate them.

Given that she came from ordinary humans, how does this work?

There is vague mention of "magical genes", though the exact heritability is not rigorously fleshed out. We can conclude that it isn't simply dominant or recessive, as both squibs and muggle-borns exist. It is generally surmised that muggle-born wizards must be the descendents of at least one squib, likely several generations back.

How did they know to go to Diagon Alley to get Hermonie’s wizarding supplies? How did they know how to find Diagon Alley?

For muggle-born students, a member of the Hogwarts staff hand-delivers the letter and explains the situation to both the student and their parents. A staff member would also accompany the family on their first trip to Diagon Alley, like Hagrid did for Harry.

Did they pay for her books? How did they pay for Hermonie’s supplies with British Pounds, since they obviously don’t have wizard money?

There is a short paragraph in Chamber of Secrets in which we see Hermione's parents exchanging Pounds for Galleons at Gringotts.

If there’s a financial aid program, why didn’t it help Ron?

The only time we see any sort of financial aid program at Hogwarts when Dumbledore visits the young Tom Riddle at the orphanage. Ron was poor, but not an orphan without financial support. Molly and Arthur could afford Ron's school supplies, just not brand-new or top-of-the-line ones. There's probably a deeper discussion to be had here on why "poverty" even exists in the magical world.

Why did they even humor the idea of a Wizard School wanting to teach Hermonie magic instead of writing it off as a joke or scam? How is it that Hermonie immediately started studying and completely skipped the “Holy shit, magic is real!” phase that should naturally come with all of this?

I feel like if Professor McGonagall shows up at your house and transfigures your table into a pig and back again, the evidence would be quite convincing :)

The staff member would likely also inquire as to what accidental magic the child has already exhibited. For many families, it is likely a relief to learn that their child's "strange powers" have an explanation, and that there are schools dedicated to refining and honing those powers.

For the muggle-borns themselves, they may have noticed that they were able to do things other children couldn't, but not have known that it was magic. So the revelation would be more of a "oh, so that's why I can do that" as opposed to "holy shit, magic is real".

A couple nitpicks:

Hermonie

Hermione

she is a witch despite coming from a No-Maj family

No-Maj is an american term. Since Hermione's family is British, they are muggles :)