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mitsuwao23Her people undoubtedly drank from clay jugs and hollered for Paw when the vittles were ready.
OK. Let's take this approach:

Her people = The people of the community she was raised in (and was part of)

undoubtedly = almost certainly

drank from clay jugs = (were the type of people who) drank from clay jugs

and hollered for Paw = and would (be inclined to) yell "PAW!!!" at the top of their lungs (to call him to dinner)

when the vittles were ready = when (the mother had finished preparing the meal and) it was time to eat.

The sentence is not about the actions of any specific individuals.

It's a general statement that says she reminds Sedaris so much of a hillbilly that he [believes/imagines] that her [relatives / community / cultural group] were probably the kind of people who regularly did the things that hillbillies typically do.

Ohhh, then there's no wonder again.

Thank you for taking your time for this. I very much appreciate your help.

Students: Are you brave enough to let our tutors analyse your pronunciation?

Just wish to point out that I had exactly the same queries as mitsuo3 about this sentence and
reached this forum through googling it ( wonders of the web and google search -never cease to amaze me..)

I closely identify with mitsuo3's need to fully understand the sentence and its idea
and wish to add my appreciation of Califjim's patience and wonderfully comprehensive explanation