Walking past the ballroom doors, it wasn't possible not to notice the music. And in Bethan's case, it wasn't possible to walk past without sticking her head through the doors to see what was going on.
When she saw her friend dancing, she grinned and slipped into the room, figuring that Chandika wouldn't mind if Bethan hung around and watched her for a little bit. She was lovely to watch - incredibly graceful and sensual - which thought had Bethan blinking slightly and wondering where it had come from, but then, there was no reason she shouldn't notice that, right?