Lawrence, 25, said she and the 34-year-old "Trainwreck" star are creatively made for each other, reported the New York Times.
"Amy and I were creatively made for each other. We have different flavors. It's been the most fun experience of my life. We're almost done writing. It just flowed out of us We've got about 100 pages right now."
The actresses, who recently vacationed together in Martha's Vineyard, only met a few months ago.
"I emailed her after I saw 'Trainwreck' and said, 'I don't know where to get started. I guess I should just say it: I'm in love with you'. We started emailing, and then emailing turned to texting... We really hit it off, to say the least."
Mid-interview, Lawrence texted Schumer that she let their secret slip. "I wrote, 'I just spilled the beans to The New York Times. Is that OK?'" she said.