It depends on what rinnie means by “divine assistance.”
Aquinas certainly thought that everything–including existence–is the result of divine action. We exist–and certainly we know–because God is acting in us.
However, he believed that God establishes and works through natural laws, and as you say he believed that a great deal is knowable through these natural means that God has established.
Aquinas rejected the view held by Augustine and many of the earlier scholastics (such as Bonaventure) that knowledge of any kind is possible only through direct “divine illumination” in which you know the divine “idea” of the created thing in question.
Like you, I initially concluded that rinnie was adopting something more like the “Augustinian” rather than the “Thomistic” view. But as I said the language she used is capable of several interpretations, and of course this is a fairly abstruse philosophical/theological issue.
What does need to be clarified–because a lot of people get this wrong about Thomism–is that no knowledge of any kind, indeed nothing of any kind, is possible apart from God. Natural law and natural knowledge do not exist independently of God, but rather are a created order that God has established and pervades from moment to moment. They exist only by participating in God.
One other note: the meaning of the term “supernatural” is one of the major “hot spots” in Catholic theology of the past half-century or so. It remains an issue on which much work needs to be done. Henri de Lubac challenged the standard “Thomist” understanding (including whether this understanding was really that of St. Thomas) in 1946, and the debate still continues. In many ways I’d say that this rather abstruse issue lies behind a lot of the more obviously “hot-button” issues debated within Catholicism.
Edwin