Stan took the news... Oddly. On one hand wow his Twin he lived his whole life was wasn't his Twin so his parents tried to cover up the death of his actual Sister! On the other hand his Twin he lived with his whole life was rather special, and those weird feelings he was starting to feel towards his sister isn't that weird right? He spent a bit more time out of the house as he was figuring out how to process everything. Meanwhile Sara's changes in her maturation started ramping up. Her fleshy tail was now about a foot long and her curved horns started poking out of her hair. Sara was expecting the horns and tails, but to her the more concerning changes were ramping up as she was borrowing Mom's underwear now as her breasts and hips swelled. Her body growing more voluptuous over the week, her hair gaining more volume, and this weird scent she started to emit that Stan and Dad seemed to really like... Sara wasn't thinking like a Nymphomaniac even a little which helped her come to terms with her changes, but what if it came later? Or what if it came as soon as she kissed a boy or something?
Dinner was served, a nice Stew that the family had enjoyed for a long time. A place where food was the center of attention and neither Stan nor Dad were taking a keener eye on Sara. Sara's eyes were a bit glazed over as she slowly put bits of Stew into her mouth, and Stan asked "Are you doing alright Sara, you seem less energetic recently?"
Sara said "Must be the... Succubus thing... taking a lot out of me... All the more reason to eat and get my strength." Sara tried to smile as she was forcing the Stew into her mouth... She could still taste the Stew, but had no desire to swallow it... Yet she felt really famished... She continued to swallow more and more of the Stew. She must not be eating enough. Sarah left the table abruptly as she left for the bathroom. She opened the door and thankfully it seemed like either Dad or Stan left the toilet seat up which let Sara let the contents of her stomach go. The girl wasn't getting what was wrong with her, was she eating too fast? That didn't seem right as she was just shoveling a spoon every minute it seemed. Stan was eating so much more so much quicker so how could she not? She felt someone hold her as she was throwing up what little was in her stomach and holding her hair back. Sara was finished and hit the plunger as her stomach contents flushed down the toilet.
"Don't worry Sara, I'll bring you up to our room and I'll call the doctor to see what's wrong with you." her mom said as Sarah's eyes started to drift into sleep.