So this girl is Lindsey Sterling, and she is amazing. She makes music videos on youtube, and collaborates with some awesome talented people. One of her recent videos, a cover of Radioactive - Imagine Dragons, collaborates with Pentatonix, a singing group. They try to look cool in the video, but I really don't buy into it. But, getting past that, I enjoy listening to it. Now, it doesn't hurt that there's a cellist... But really, Lindsey is so, so, so talented: how many violinists do you know that can dance while playing? Her channel is Lindseystomp, you should check it out.