The only rare occasions Clawdia, or just about any mob "not showing up", were I was lagging. The mobs were actually there physically but not visually. Typically, updating graphic drivers, and relogging will make them appear again. If not, then perhaps choose a lower graphics setting if you are using an older computer.
It's possible the boss wasn't rendered properly on your game client. try logging off and then logging back in so clawdia appears. She has lots of health so plenty of time for you to do this.