You do nothing noticeable. Endure it, while looking at your sister inquisitively while she listens. When she asks, say nothing and turn away. When she turns away, repeat the process.
Mindfuck is always the best solution.
PS If she turns up her player loud enough, then you should be able to tell.
PPS If she starts singing their songs out loud or goes on about how dreamy one of those whorebags is, you have permission for LTL force.