The 29-year-old actress created the account to understand her character in the fictional Fox News reporter Kayla Pospisil in Jay Roach's upcoming drama "Bombshell".
"I didn't grow up watching Fox News, and I didn't grow up in the same place as (Kayla) I was struggling to understand that point of view for a while, and Twitter ended up being the most useful tool," Robbie told ew.com.
"Because people are extremely vocal on Twitter," she added.
"Bombshell" chronicles the downfall of news titan Roger Ailes (essayed by John Lithgow), whom multiple Fox employees accused of sexual harassment. Ailes denied all the claims until his death in 2017.
It follows Fox's most famous female faces as they grapple with their own experiences with Ailes, including Megyn Kelly (Charlize Theron) and Gretchen Carlson (Nicole Kidman).
Talking about her role, Robbie said: "Kayla is an amalgamation of many women's stories, and some of the specifics you see in scenes with her are taken from real-life interactions those women experienced."
Robbie has herself has spoken out against harassment in Hollywood, and joined others in the wake of the #MeToo movement. She has admitted that making "Bombshell" opened her eyes to how insidious it can be.
"I felt like I've done nothing but talk about sexual harassment in the workplace, and I thought that I had a pretty comprehensive understanding," she said, adding that "Bombshell" showed her that even victims of sexual harassment don't always recognise it and an unspoken culture of silence can help perpetuate it.
( With inputs from IANS )