The 'RHOA' star announced she's getting super serious with a guy she's been dating for just a month -- surprising enough -- but the bigger shocker is the guy is Falynn Guobadia's ex, Simon.

If ya don't know ... Falynn just revealed her split from Simon last month, after 2 years of marriage, saying a "mutual decision was not made lightly." And, she and Porsha are supposedly good friends -- or at least that's what 'RHOA' fans thought considering Porsha brought Falynn on last season as a "friend of the show."

However, Porsha blew up that notion when she announced on IG, "Our relationship began a month ago -- yes we are crazy in love. I know it’s fast but we are living life each day to its fullest."

She adds ... "For all of you that need facts, I get the optics but Simon filed for divorce from a previous marriage in January. I had nothing to do with their divorce filing. That’s between the two of them."

And for the kicker, Porsha claims ... "Falynn and I are not friends, and Simon’s divorce has been settled."

Now, she stopped short of saying she and Simon are engaged in her post, but Simon confirmed that later on his IG. Porsha also claims her ex, Dennis McKinley -- to whom she was previously engaged -- is supportive of the situation.