Frequent readers of Totally Covered already know who Lena Katina is. Longtime readers of this blog know she's been here before.
For the rest of you - Lena Katina was one half of a Russian duo named t.A.T.u., who played up a public lesbianism that wasn't real (evidenced by her bandmate's deeply homophobic statements about a decade later). After t.A.T.u. went on hiatus to pursue solo careers in 2009, Lena took full advantage of the shot and made some really good pop music.
I don't think it takes a genius to know that this song is about the death of t.A.T.u. No, Yulia, her bandmate, isn't dead - but they didn't end on great terms (but did reform in 2014 for the Winter Olympics). The song, from 2011, was Lena's debut single and her biggest hit to date. The video itself is a funeral for Lena and Yulia, as a symbolic and respectful end to t.A.T.u. It became a worldwide hit.
Of course, this being a member of t.A.T.u., there is an uncensored version of the video.