Her name is Kaitlyn Conover. She is Josh's ex-girlfriend. Her first mention was in "GRANDPA COMES HOME!" when Michael mentions her because Angry Grandpa and Josh had "The Talk". She appeared in one of Charlie Green III's videos, two of Michael's videos, and a couple of Jennifer's videos. She also insulted Jennifer's terrible Christmas Ham. She also claimed that her and Josh (Better known as Jay, or simply JC) planned on starting a YouTube channel. Their ship name is Jolyn (JOE-LIN, 'Jo' for Josh, '-Lyn' for her name). She is 16 years old, the same age as Josh.
Her and JC broke up sometime on or before March 9th, 2018, as stated by Jennifer in one of her livestreams when Kaitlyn started watching the stream. She claimed during the stream that she was going to private it, but it is still public (As of this edit). Even though the stream is still up, you cannot view her comments from the live chat, as they have been deleted. During the same stream, she said things about "Exposing (them/Josh)" and was saying mean things, but the messages quickly got deleted. However JC claimed that he didn't tell her anything. I (the user making these edits) was only able to save one of her comments, image below. She did also post another comment that I was unable to get a screenshot of, but did copy the comment: "Hey jen look after your children please .....".
She also has a YouTube channel called "Kaitlynskute korner"