Friends with benefits bishova where Kate falls deeply in love (of course) and is just constantly yearning and pining for more from Yelena. She hides her feelings the best she can, but she loves Yelena so much and loving Yelena, having some of her but not all of her, is eating her up inside.
And Yelena ... Yelena knows.
Kate isn't good at hiding her feelings, but while Yelena likes having sex with Kate and even really likes Kate (perhaps even loves her back), but she doesn't want to have an actual relationship with her. So she selfishly continues to sleep with Kate even though she knows that each time she leaves afterwards, Kate cries into her pillow. Sometimes, she feels guilty about it and thinks she should cut Kate loose, give her a chance to move on, but she can't stay away from Kate.
And the thought of Kate fucking anyone else, let alone loving anyone else, also fucking enrages her. I imagine their arrangement isn't exclusive, and Yelena probably sleeps with other people. (Especially since she's only in New York some of the time.) But Yelena just absolutely cannot stand the possibility of Kate seeing anyone else.
At first, Kate isn't even interested in doing that, but then she starts to go on dates, and she begins to recede from Yelena (texting her less—poor Yelena misses receiving her nudes of Kate 😥) as she tries to move on. She can never actually say no to Yelena—she doesn't want to—but she tries to pull back emotionally and Yelena can tell and she absolutely hates it.
She refuses to allow Kate to move on.
She sabotages her dates, in a variety of creative methods (only some of which involve blatantly threatening the date), and she also acts more intimately and flirtatiously with Kate outside of sex. She uses more petnames, is affectionate, and acts almost like a girlfriend but not quite.
Kate is so confused by all the mixed signals, and it pains her so much. But Yelena basically dangles the possibility of a real relationship in front of Kate like a carrot on a stick.
Just Yelena being a toxic and overall awful person to Kate because she doesn't know how to express her feelings in a healthy manner uwu 💖