It appears now she was not ejected. That's what the Bernie crowd was first saying. She simply was not allowed to introduce Bernie Sanders to speak. This was probably because the DNC could not trust her to use the podium to make another inflammatory remark against the DNC or Hillary Clinton like she was doing daily on MSNBC.
Of course, this gave rise to new protests as Nina supporters like Susan Saranden wore buttons, "I'm with Nina" while staging a sit-in at the media tent.