Don't listen on trolling commentaries, from what you achieved is already a great starting point. The story would do well with some formatting though.
It needs to be separated in paragraphs for easier reading rather than a wall o' text.
Also if you are adding too many characters talking at the same time it would do best with adding their names like in a play:
You:
Mistress Whatever:
Sister:
and so on
From the story of what I read it seems you wanted to add two voices brother and sister but the colour only is not helping.
Also you may want to add gifs and many images as you can... Don't. Keep it simple and work from that. Make every interaction count, rather than a slideeshow scrolling fest
Write what you want, if later you want to ask for suggestions do so. But keep it clear that the foundation of the story is this one and not other..
Adding two perspectives is really difficult. Adding two characters is even more difficult. Its means double amount of writing and keeping track in TWINE of what is what and who is who. I know I've made that mistake when I started my first project. It was too big to handle...
So the story would do good, after the intro to focus only on the player. Going to Dominatrix classes shouldn't be on the schedule if the player is going the sub route. And if that's the only scenario - which I'm sure is what is being hinted on, you would do good with working through that. Rather than complicate yourself.
If you do want to complicate yourself... Once the player goes to sleep, it could be added in a passage of the Female POV AKA your sister, going to the dominatrix class. But more of a recollection
Keep up the good work, and if you need any help keep in touch. I'm trying to also write something in TWINE and it's been ages, but I know the framework.
