The real-life inspiration behind Netflix's new hit series told Daily Record she's hoping for a seven-figure payout after claiming to have only received about $313 for the sit-down seen round-the-world ... in which Fiona suggested Richard Gadd had defamed her in his show.

She says ... "I asked if that was what they paid everyone and, if so, I wanted to see documentation to that effect. That documentation has not been forthcoming. I have not signed a contract for the interview and I will be seeking far more than a piddling £250."

Fiona also slammed Piers for pretending to be on her side, calling his empathetic demeanor during their interview "all a big act." She added ... "He didn’t even say goodbye and only got the photograph taken with me because he needed it for the publicity."

All in all, Fiona said she's planning on formally demanding £1 million (around $1.25 million) from Piers and co. ... in addition to her plans to sue Netflix and Dick. In other words, it sounds like she's threatening a lawsuit -- unless, of course, they wanna settle.

Remember, Fiona's "Baby Reindeer" character, Martha, is portrayed as a deranged stalker obsessed with comedian Donny Dunn, played by Richard ... sending him thousands of emails.

She then told her side of the saga to Piers -- where she downplayed and/or outright denied several of the claims made about her character -- which was viewed by millions of people.

As for Piers' stance on the interview ... he issued a statement on Thursday, where he claimed Fiona lied during their interview.

He wrote in The Sun ... "There were moments in the interview where my suspicious alarm bells rang loud, especially when she suddenly said, 'Even if the email thing was true, the rest is not.'" So, yeah ... sounds like he feels like she wasn't entirely forthcoming in their chat.

Despite this, Fiona is capitalizing on her "Baby Reindeer" fame elsewhere ... as she's set to make a club appearance at Coventry's Kasbah Nightclub. The promotion promised a personal appearance by Fiona ... who might "take some lucky reindeer home to hang her curtains."