A call between her and US Ambassador to Ukraine, Geoffrey Pyatt was leaked on YouTube. It showed the US meddling in the Ukrainian elections.
https://www.bbc.com/news/world-europe-26079957
This site claims they were outright trying to topple a duly elected President Viktor Yanukovych (sound familiar?).
Check out their method of choice:
>To sell this latest neocon-driven “regime change” to the American people, the ugliness of the coup-makers had to be systematically airbrushed, particularly the key role of neo-Nazis and other ultra-nationalists from the Right Sektor. For the U.S.-organized propaganda campaign to work, the coup-makers had to wear white hats, not brown shirts.
>So, for nearly a year and a half, the West’s mainstream media, especially The New York Times and The Washington Post, twisted their reporting into all kinds of contortions to avoid telling their readers that the new regime in Kiev was permeated by and dependent on neo-Nazi fighters and Ukrainian ultra-nationalists who wanted a pure-blood Ukraine, without ethnic Russians.
https://consortiumnews.com/2015/07/13/the-mess-that-nuland-made/