Josy does have a storyline and yes insecurities are a storyline but lets put that to the side. Would you say Sage has a story? If the answer is yes then that also means Josy has a story how you ask they share every single storyline Sage has Josy has and in fact Josy had it first the only one Josy doesn't share is president of the hots everything else is the same. Some will say most of Josy story takes place before the game, I don't care it still counts just the same
If you just look at it as they both are cheating on their gay partner, I can see the similarities. But then Sage moves on from Chad into a real relationship with the MC while Josy is in a three way lesbian fantasy.
But beyond that Sage is so much more, she's the president of a sorority full of girls who whore themselves out with her own father a client and IMO the mastermind of it all, I believe Quinn is the current chef and that Burke has had a girl in the sorority that has been entertaining his rich friends for years.
Another similarity between them is the divorce of parents but let's be honest, we will never see Josy's birth mother and probably not even Monica where as Jade is a major character and one we can actually bang. Jade's divorce will be a major plot point and Sage is right in the middle.
Outside of Maya there isn't anything major for Josy to be involved in other than as a friend, which is kind of all she is for Maya too.