Kelly is one of the main characters of the episode "San Junipero" of Black Mirror. We meet her as a beautiful, outgoing party girl.
At a nightclub in San Junipero, Kelly propositions a young woman named Yorkie, but Yorkie flees. The next week, Yorkie returns and sees Kelly flirting with a man. Kelly and Yorkie end up hooking up back at Kelly's beach house.
As they continue to run into each other, we learn that San Junipero is a simulated reality. Kelly is, in fact, an older widow who had a long and happy marriage with her husband. Yorkie is paralyzed and wishes to be euthanized but needs the consent of her parents (who won't give it) or a spouse. Kelly proposes to Yorkie so that Yorkie can be permanently uploaded to San Junipero.
Kelly doesn't want to be uploaded when she dies. Her husband chose not to be uploaded because their daughter had died before San Junipero existed. Yorkie is devastated to learn that Kelly is planning on leaving her.
Eventually, Kelly changes her mind and decides to enter San Junipero permanently, and Yorkie and Kelly are reunited.