Does my laughing at and listening to my friend’s mockery—who joked about ants breaking dishes—count as mockery that expels one from the faith, knowing that I tried to suppress my laughter but failed, and am I sinful for not denouncing her?

The questioner is suffering from obsessive thoughts about mockery (istihza'), and she must cast away these thoughts and not indulge them. Obsessive thoughts are a severe illness and a chronic disease, and indulging them leads one into confusion, pathological doubt, distress, and legal difficulty.

The questioner should not be obsessive, accusing herself of disbelief every time something happens. It is enough for her to condemn what she knows to be wrong without delving into whether it constitutes mockery that expels one from the faith or not.

Explicit mockery of religion and its rulings did not appear in the two incidents mentioned in the question. The first incident was a jest related to explaining how ants cause harm and how it occurs. The second incident is not primarily understood as mockery of the ruling on backbiting and its comparison to eating the flesh of the deceased backbiter, even though the act itself—backbiting and what followed it—is forbidden. However, it does not reach the level of mockery of religion that invalidates faith.

Mockery of religion stems from ridicule and contempt. The questioner's fear—which has reached the point of obsessive thoughts—is a clear indication that she has no contempt whatsoever for religion and its rulings. The best cure for her condition is to completely turn away from obsessive thoughts.