'Mean Girls' OG Author Slams Tina Fey ... Threatening Paramount???

The lady who inspired "Mean Girls" is pissed Tina Fey and Paramount have cashed in on her work while she's been left with zilch ... and now, she says she's doing something about it.

Author Rosalind Wiseman told the NY Post this weekend that she and her lawyers are circling legal action to examine the movie studio's accounting books in order to figure out if there's money they've made from 'Mean Girls' over the years that could be sent her way.

The reason ... Wiseman says she feels like she's been screwed out of a lot of potential cash since the hit 2004 film was released -- especially in light of the Broadway musical that's been made about it ... which has done fairly well for years now in different markets.

According to RW, the deal she signed with Paramount and TF at the time -- which made her a one-time $400k, and which she acknowledges relinquished any rights to the work and/or derivatives -- guaranteed net profit points, meaning she could make more based on how well the flick did. However, she claims Paramount has, time and again, told her there's nothing left of the pie for her ... and that they haven't actually collected much from it long-term.

Wiseman thinks that's BS -- and her attorney, Ryan Keech, says, “I suspect most people would be shocked at how shabbily Rosalind Wiseman has been treated. And properly so."

He adds, "It is nothing short of shameful for a company with the resources of Paramount to go to the lengths to which it has gone to deny Ms. Wiseman what she is fairly entitled to for having created what has become one of the most iconic entertainment franchises of the last 25 years." Rosalind and co. say they want to audit Paramount, and are considering further next steps ... although they don't specify exactly how they'll get Paramount to comply.

As many people know ... 'Mean Girls' is based on Wiseman's 2002 parenting book, 'Queen Bees and Wannabes,' which Tina read and thought could make for a good script.

Of course, she was absolutely right ... the movie became a cult classic, and serves as a staple of the 2000s. Thing is ... Wiseman sounds salty about how Tina Fey has repurposed the material throughout the years, alleging TF's even roped her into appearances and workshops (regarding smaller 'Mean Girls' plays) without paying her an extra cent.

She says, "I’m clearly recognized and acknowledged by Tina as the source material, the inspiration. I’m recognized and yet I deserve nothing?"

Wiseman adds, “Tina’s spoken so eloquently about women supporting other women, but it’s gotten increasingly clear to me that, in my own personal experience, that’s not going to be the experience. You don’t just talk about supporting women, you actually do it."

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