Is this the first time she hasn't eaten? Hmm...if you feed them tomorrow and she doesn't eat, look for any rubbing against objects, rapid breathing, and excess mucus. There is a very common disease called "brooknella" that affects clowns. It's actually a parasite. I don't want to worry you but to make you aware so if it is infected you can catch it before it would kill her. If by chance she is infected then QT both as its contagious...but for now, try to feed some brine shrimp tomorrow to see if she will go for that and watch her closely.