Harold Wentworth & Stuart Flexner, Dictionary of American Slang, first edition (1960) has entries for both trumped-up (as an adjective) and trump up (as a verb phrase), indicating that the terms were in U.S. slang use when Donald Trump was still in Buster Brown shoes. Here they are:
trumped-up [or] trumped up adj. Made up, imagined; hence, false. 1952: "He had to flee ignominiously with a trumped-up explanation, for how could he confess the simple truth?" C[onrad] Aiken, Ushant, 187.
trump up To make up something out of one's imagination, as a lie or alibi; to make something out of makeshift ingredients or parts, by using one's ingenuity; to use one's imagination or ingenuity to make or create something.
Clearly the first meaning of the verb phrase is a lot less attractive than the the next two. But that negative meaning is the one that has persisted in common usage of the verb phrase; and the sense of the adjective phrase has, if anything, gotten worse. Robert Chapman & Barbara Kipfer, Dictionary of American Slang, third edition (1995) omits "trump up" from that edition of the dictionary but has this entry for the adjective phrase:
trumped up adj phr by 1728 False; concocted; fabricated; =PHONY: The indictment was trumped up for revenge
This is precisely the sense of "trumped up" that Hillary Clinton was trying to suggest in the quoted phrase "trumped-up trickle-down [economics]." You might translate the whole expression as "phony help-the-poor-by-rewarding-the-rich economics."
As you may know, "trickle-down economics" is a sort of hostile alternative metaphor to "a rising tide lifts all boats." The notion is that if the government designs its economic policy to benefit the rich, all other classes in society will eventually benefit as well, as the rich invest their windfall in innovative business ventures, yachts, fancy parties, campaign super-PACs, and other forms of "job creation." "Trickle-down economics" became a common term during Ronald Reagan's tenure as President in the 1980s, reflecting the Reagan administration's vigorous championing of supply-side economics. As the Wikipedia article on trickle-down economics observes, however, critics of that policy tended to use the term far more often than proponents did.