Kelly sucked.
Kelly was an @$$h013. Yorkie should of broken up with her.
She actually slapped Yorkie in the face just for asking her to stay in San Junipero.
This was because she was ranting that Yorkie couldn't possibly understand being in a relationship and marriage, and the experience that she had. The audacious thing about this was that this was after she had learned that Yorkie had been in a coma since she was 21. And also, Yorkie just asked. It's not as if she put a lot of pressure on her.
She probably did all of it just for the drama, but the significance is she proved she didn't care about Yorkie at all and that she had no understanding of her or her life experience. Also, Yorkie was such a down to earth stable person reacting in such a dramatic fashion was really over doing it.
Then, after she said she only proposed to her to be nice which was pretty cold, she sped off like the world's biggest diva.
Kelly was clearly just a big drama queen. She made a point of saying that she was insincere, immature and completely lacking in empathy. After chasing her around through every time period, Kelly was nothing more than one night stand material.
I would of taken the car crash as karmic revenge and broken it off with her while she still writhing on the ground.
A much better episode of Black Mirror would of been, if they had gotten together and they were together in the after-life once Yorkie had realized this epic mistake and the horror of being stuck in eternity with someone as vacuous and full of it as Kelly.