Heres two songs(well covers of songs) that make me think of Cassie. :)
Radioactive! I think this is her theme song haha. I like this cover cause its what I picture her voice being like. Of course the original song is better though.
[youtube]P6qFCqOy3HU[/youtube]

And this one too. Its by the same person XD
[youtube]MJenMcukwuI[/youtube]