The Green Party candidate provided documents related to communications with officials tied to Russian media organizations and the Kremlin, as well as documents related to Stein’s 2015 trip to Moscow, which included a dinner hosted by RT that was also attended by both former Trump administration aide Michael Flynn and Russian President Vladimir Putin.

But the campaign objected to the committee’s request for communications with “Russian persons, or representatives of Russian government, media, or business interests,” arguing it was broadly targeting the communications of people “because they happen to be Russian immigrants or of Russian descent.”
 
…Stein has been connected to the Senate panel’s investigation into Russia’s 2016 election meddling in part because of her appearance at a now-infamous dinner that was hosted by RT, the Russian television network. Flynn, President Donald Trump’s former national security adviser who has since pleaded guilty to lying to the FBI, was sitting at a table with Putin at the dinner — along with Stein.

…Stein has not been accused of wrongdoing or colluding with the Russians. But her political views often align with the Kremlin and mirror talking points heard on Russian state TV: She claims the American political system is rigged, opposes the notion of American exceptionalism, is a vocal critic of US military operations overseas and downplays the impact of Russian meddling in the 2016 election.

Jill Stein’s campaign objects to Senate request for some Russia documents – CNNPolitics

If she has nothing to hide, she will hide nothing.