It's the small words make all the difference.

If "or" actually equates to standard English "ere", then She'll beg or she work, and she'll play or she beg, means something like
    She'll beg sooner than work, and she'll play sooner than beg

And if "an'" is the equivalent of English "if", then If you give her good measure as long as a sheep-foot, and with the girth of a goose-egg is a description not of her own "equipment", but of the "equipment" that you must bring to her.