CNBC isn't the first place you would think to find Jessica Simpson, but the former pop star has been making the press rounds this week celebrating the 10th anniversary of her wildly successful Jessica Simpson Collection fashion line, worth somewhere around a billion dollars. So she sat down for an interview with "Closing Bell" co-anchor Kelly Evans.

Simpson wasn't very specific about her financial success when Evans asked about the company's evolution and her investment choices ("I don't always know where all of my money is, but there are people that I love that know where all my money is.") However, she did provide a candid answer when Evans inquired about her biggest money mistake, either personally or professionally.

"The biggest money mistakes? Hmmm, I don't know," Simpson said. Then she laughed: "For some reason, I thought of my first marriage."

"That's actually a common answer, believe it or not!" Evans responded.

Wait, why the slam against Nick Lachey? The two have been divorced for nearly a decade and are both happily remarried. But if you look back far enough, their financial situation was actually a pretty hot topic for awhile back when the Simpson-Lachey divorce rocked the celebrity world.

The superstar pop couple were everywhere in the early aughts, thanks to gaining fame on MTV's "Newlyweds" that chronicled their daily lives. One of the first reality shows of its kind, many were fascinated and made predictions about their future — so it caused a media storm in November 2005 when they announced they were splitting up.

The most contentious point: The money, given that they didn't sign a prenuptial agreement. "Under California law, the couple, who did not sign a prenup, must evenly split all assets acquired during the union," People wrote at the time. "With Jessica's income outstripping Nick's, that may prove a sticking point."

The magazine reported that thanks to her endorsement deals and burgeoning clothing line, Simpson was worth $35 million; as opposed to Lachey, whose solo career mostly flopped after his band 98 Degrees dissolved, and made closer to around $5 million.

The rumors went back and forth, about how much Lachey wanted, and who convinced them not to sign a prenup in the first place. (A "source" told People that Simpson's father/manager urged them not to sign since Lachey was worth more when the two tied the knot in 2002.)

A little less than a year after divorce papers were filed, TMZ reported that Lachey settled for "considerably less" than half of their combined earnings to "avoid an ugly court fight." But given Simpson's comments that it was her biggest financial mistake, it was clearly an amount that made an impact.