Despite what she said last week, JESSICA SIMPSON was NOT "extremely happy" when she heard that her ex-husband, NICK LACHEY, was engaged.

--How do I know that? Because on Thursday . . . several days after Nick announced he and VANESSA MINNILLO were engaged . . . Jessica got engaged. (!!!)

--Jessica's rep confirmed Friday that she and former NFL tight end ERIC JOHNSON are getting married. There's no word on a wedding date. Jessica and Eric have been dating since May.

(--Sure, it's entirely possible that their engagement was borne out of nothing more than their love, and their assurance that they are, indeed, meant for each other. But how PROBABLE is it?)

--Jessica showed off her engagement ring during an appearance on Saturday. It's a ruby flanked by two diamonds.