"Triflin'" is one of my favorite African-American slang terms, and a quick Google reveals that this quote was indeed taken from a column written by an African-American, Michelle Singletary. Slang dictionary definitions on the internet are all over the place for the exact meaning of this term, but I've always understood it to mean unserious, lazy, and generally worthless. Some of the internet dictionaries also define it as "deceitful," which makes sense in this context. People failing to pay their bills aren't lying because they're too lazy to earn the money; they really need help.