I do not think that the maid of verse 19 refers to the adulterous woman of verse 20 for the reasons I state below.
First, assuming that the above translation is faithful to the Hebrew, it seems that punctuation - which was not in the original manuscripts - might makes a difference here.
The JPS Tankakh translation of these verses reads:
Proverbs 30:18–20 (Tanakh)
18 Three things are beyond me;
Four I cannot fathom:
19 How an eagle makes its way over the sky;
How a snake makes its way over a rock;
How a ship makes its way through the high seas;
How a man has his way with a maiden.
20 Such is the way of an adulteress:
She eats, wipes her mouth,
And says, “I have done no wrong.”
The Oxford Jewish Study Bible commenters claim that verse 20 is in contrast to verses 18-19, in that the movements of the first four (eagle, snake, ship, man with a maiden) are graceful, but that of the adulterous is crude and shocking:
The wonder of the “ways” or movement of the eagle, the snake, and the
ship may lie in the fact that they do not leave traces or that they
are smooth and graceful. As for the way of a man with a maiden, love
is a mystery, but just how it is mysterious is left to the
[Verse 20] seems mechanically tacked on and inappropriate, but it
might be intended as a shocking climax. The four “ways” are mysterious
and graceful and leave no trace. The way— that is, behavior— of the
adulteress too is especially amazing: She is unbelievably smug and
thinks she can wipe her sin away as if wiping the crumbs off her face.
The Jewish Study Bible (2nd ed.) (Kindle Locations 91028-91030, 91032-91034). Oxford University Press. Kindle Edition.
Further, it seems quite possible that the original Hebrew doesn't even refer to any maiden in verse 19.
The Septuagint version (compiled in 2nd cent. BC) of verse 19 makes no reference to any woman, but rather refers to the road of a man in youth. Either the proto-Hebrew of the Septuagint text is much different than that consulted by the Masorete transliterators (compiled in the 8th cent. AD), or perhaps the Masoretes ended up vocalizing the Hebrew to produce a much different meaning. The Hebrew text that Jerome translated from (4th cent. AD) also seems to be different from the later text consulted by the Masoretes and agrees with the Septuagint (... viam viri in adolescentia).