She did not disclose the identity of the individual they were searching for because they were here on a secret mission. It was not because she didn't trust them. Every member here belonged to the same faction and was someone that could be trusted.
In any case, even if she told them, they would either not believe her or would be too afraid to dive inside the dungeon. Simon's infamy when he left the capital was earth-shaking, his achievements and the mark of battle that he left behind was still there.
Those who had witnessed the battle that day spread the news everywhere and by now everything was so exaggerated that some facts were no longer the truth. Everybody feared that mysterious demon that had turned their capital upside down.