When the player clicks/taps End Game in any of the boss levels, she will appear at the middle of the screen and throw her green jelly at the screen before the level failed screen appears.
However, when you hold an X at the gold shop screen or hold End Game at the option to continue the game or end the game, there is a chance that she will not appear and the level failed screen will appear immediately.
She appears in the main menu of the game. However, she was removed on July 9, 2019. After March 15 2022, she came back with a new main menu.
She initially appeared in level 4 before March 2017, when those previous levels were Jelly boss (this change was not updated completely before March 2018).
She is a playable character in Candy Crush Friends Saga. In that game, however, she did not do anything bad, and she gains a pendant of a light blue candy.
In episode 86 of Candy Crush Soda Saga, Northern Nibbles, character Reseacher Toco does mention Jelly Queen, but it does not tell her name; instead, it says "Jelly lady".
Her jiggling was changed on March 24, 2021 on mobile devices and April 6, 2021 on Facebook.