It's something that has meaning to Jaye, it shouldn't be important but to her it is.Honestly, it's entirely irrelevant that the sex with Tara happened years ago but Jaye only read about it a few days ago.
Has nobody ever met someone IRL, be it man or woman, that would bring random shit from ages ago up just to "score points" in an argument or imaginary competition? This happens all the time with some people.
It is afterall(no matter how long ago) her BFF and the guy she's been in love all of her life, it happened 5 years ago, yes, but she probably still thinks about it... hopefully now she can let go.