Michael Phelps -- Alleged 'Ex-Girlfriend' Is Ready for Her Porno Close-Up

The formerly intersex woman who claims she was nailing Michael Phelps ... is on the verge of getting nailed in her first porno ... TMZ Sports has learned.

Taylor Lianne Chandler is in Hollywood fielding an offer from Vivid Entertainment honcho Steve Hirsch -- who tells us he wants her to star in one of those ever popular porn parodies.

Taylor made headlines last month when she claimed she and Michael dated after meeting on Tinder. You'll recall ... Taylor was born with male and female organs, but says she's since had surgery.

We're told the proposed porn would be loosely based on their alleged relationship. Think, "When Harry Met Sally" ... with way more nudity. And real sex.

We got Taylor on her way into Vivid HQ, and she told us she's still in the "wine and dine me" stage of negotiations. As for compensation ... she's more interested in back end, than getting huge money up front.