Bryan Freedman, who reps Nicole Shanahan, tells TMZ ... "Make no mistake, any suggestion that Nicole had an affair with Elon Musk is not only an outright lie but also defamatory." Freedman first spoke to DailyMail.

There's no further elaboration, but his statement says enough -- and that final line certainly suggests she might be considering her options right now ... attorneys don't use legal terms like "defamatory" unless they're mulling over a lawsuit.

As you know, Elon also denied the story outright after it was published this weekend by the Wall Street Journal -- taking to his favorite platform to bat it down in a variety of ways ... including suggesting it couldn't have been true, because he hadn't had sex "in ages."

He also said he'd just seen Nicole's husband, Sergey Brin, at a party recently ... and posted a photo of the two of them looking cool together. Until now, both Sergey and Nicole have been silent ... which wasn't helping Elon with his case.

Now, though, Nicole's officially weighing in -- and she, too, is claiming the whole thing is made up. It'll be interesting to see if anything more comes of this from either the subjects of the report or WSJ itself.