Along with "the foolish woman" and the assorted male fools who follow her, the adulteress is one of the main villains of Proverbs. But she isn't really a character so much as a symbol embodying all un-wisdom and unfaithfulness. She's an example of what not to do, both for the individual person and for Israel as a whole.
Whereas Proverbs and the rest of the Bible argue for a single-minded focus on one God, or one spouse, the adulteress craves variety—like a worshipper of many gods—and gets her kicks that way. So, she's not just an example of a woman cheating on her husband—though she's obviously that, too. She's an example of the wrong mindset. The Biblical authors generally recommend concentrating steadfastly and wholeheartedly on one thing, but the adulteress has numerous objects of affection.
A Bit of a Double Standard?
Proverbs gives us a depiction of her seduction technique, as the adulteress persuades a young man walking the streets at evening:
With much seductive speech she persuades him; with her smooth talk she compels him. Right away he follows her, and goes like an ox to the slaughter, or bounds like a stag toward the trap until an arrow pierces its entrails. He is like a bird rushing into a snare, not knowing that it will cost him his life. (Proverbs 7:21-23)
Of course, if you want to ask why Proverbs inveighs against the adulterous woman, but doesn't have much to say about the adulterous man, aside from seeing him as a sort of pathetic victim of the adulteress—ask away, because that's a good question. (Jack Miles also makes this point.)