The Room of the Secret Password was featured during the final episodes of Season 2 and all of Season 3. Despite it being in 53 episodes, there were only 12 contestants (over the course of 11 episodes) in which a contestant read a password aloud. Below is a list of all of those contestants.
Chandra, Leopard-Skin Cloak of Annie Oakley
Andrea, Lion-Headed Bracelet of Chandragupta
Zac, Secret Map of the Bandit Queen
Kelli, Thornwood Gavel of Judge Roy Bean
Jeremy, Golden Spider Web of Robert the Bruce
Keith, Missing Portrait of Hans Holbein
Quentin, Red Sash of Tokugawa Ieyasu
Brandi, Red Sash of Tokugawa Ieyasu
Kimberly, Broken Trident of Poseidon
Randy, Metal Beard of the Egyptian Queen
Dawn, Pearl Necklace of Gwalior
Matthew, Bullet-Riddled Handbag of Belle Boyd
Kelli has taken some heat on this site in the past for not speaking intelligibly when she read the passwords aloud. But when you look at that list, it should become apparent that she was not the only one on that list who failed to remove her mouthpiece before saying the passwords. Zac, Jeremy, Randy, and Matthew all kept their mouthpieces in as well.
The biggest difference between Kelli and the other contestants is that instead of reading the password toward the spotter with a microphone who stood in the Shrine of the Silver Monkey (see image below from "Lion-Headed Bracelet of Chandragupta, courtesy video posted on youtube.com by ChargerTheWolf), she placed the tablets on the pedestals at the front of the room and spoke looking out directly in front of her.

Why do you think the Room of the Secret Password was completed so infrequently? And what about Kelli's performance in that room (please note, I am asking about her performance, not the outcome) makes her get so much flack?