A week after unveiling the music video for her new single, "Used to Love You," [1] Gwen Stefani [2] appeared on The Ellen DeGeneres Show to sing it in front of a live audience. The song is indisputably about her ex Gavin Rossdale [3]. The two split over the Summer [4], and to be honest, we're still healing. Stefani's performance is beautiful, and it's clearly a very emotional song for her. Watch her performance, and feel her pain.