i have recently begun writing a story called futa Katie's misadventures (https://chyoa.com/story/futa-katie's-misadventures.14003) this is the first story i have written if you are interested in the story please read and give suggestions for story paths
Here's my recommendation: drop the premise of Katie ending up exposed and humiliated and recategorize the story as something like "group sex" or "bisexual", then continue much the way you have so far, three teenagers, who all have something to hide, trying to keep their triad a secret...