Who exactly is Nina Turner, and what are the electoral accomplishments that make her so....
....important that she can dictate to the President of the United States?

Let's look at her electoral history:

Ran for Cleveland City Council in 2001, lost
Ran for Cleveland City Council in 2004 for a vacated seat, won
Appointed to State Senate in 2008
"Re-elected" (ran unopposed) in 2010
Announced her candidacy against Marcia Fudge in 2012, dropped out
Ran for Ohio Secretary of State, lost
Ran for OH-11, lost the primary to Shontel Brown

She hasn't defeated a single opponent in a primary or election since 2004.

Along the way she supported Sanders in the 2016 primary, he lost
She supported Jill Stein in the General Election, she lost
She was co-chair of Sanders' campaign in the 2020 primary, he lost
After the nomination, she refused to support Joe Biden in the General Election, he won

And as noted, she called Joe Biden a "half bowl of shit" during the General Election campaign, and when asked a few weeks later about it she doubled down by calling him just a "bowl of shit" (no longer half) - that's "playing nice"? And what exactly are these "gloves" she's taking off.

In addition, in late 2020 she co-founded and was her intention to run in the OH-11 primary as a candidate of the "People's Party". But she didn't properly register it in Ohio so she couldn't. As they put it when she announced her candidacy, inasmuch as the People's Party wasn't properly registered in Ohio, she "had" to run as a Democrat, presumably reluctantly.

Soon after she lost the August primary she founded a lobbying firm, "Amare Public Affairs", with the financial backing of right wing Mercury Public Affairs, one of whose clients was a foreign nonprofit connected to Paul Manafort.

A month after announcing her new lobbying firm, her financial benefactor, Mercury, became mired in scandal.

So again, who is she to tell the DEMOCRATIC President of the United States what to do?

Finally, what is this so-called "movement" of which she always speaks? From all appearances her anti-Democratic Party "movement" is standing still.