It's true that under Oregon law a 16-year-old can't consent, but keep in mind that in most U.S. states the age of consent is 16 or 17.  If the age was chosen arbitrarily, as Oregon's was, it is probably unconstitutional.

In Washington the age of consent is 16.  It is 16 in Canada and Great Britain.  Only two European nations (Ireland and Turkey) have a higher age.  In Oregon it was 16 until some of the law revisions of 1971.   When that revision was made, the chair of the law revision committee admitted that the choice of 18 was essentially political and not based on anything factual.

So we can use the word "child" in law, but I respectfully suggest that doing so needs some kind of scientific basis, not just the fact that they had sex on this side of the Columbia River.

For my part, I'll just say that the woman behaved very stupidly and leave it at that.  I hate to see prosecution resources devoted to this kind of case when our communities have so many other problems.