You've got a good way of bringing your characters to life. A lot of people do a lot more "Telling" than "Showing" when they write.
You get inside their heads and let us know their motivations. Some of this of course, can be done through conversation, but you actually give us a look at their inner workings and personalities.
The only thing I'd like to see on the face of it, is a little more scenery. You've done great in descriptions of the terrarium, for example. If you painted the rest of the backdrops so well this would add even more amazing depth to your world.
Sometimes, it helps to start with describing the place the scene is happening in, and then the focus character of a scene. Like when you watch a movie, if the scene takes place in someone's back yard during a swim party, you might notice the pool, or a barbeque, even before you focus on the guy flipping burgers at said barbeque.
Honestly, your work is (with the minor typo demons that plague us all aside) of a higher quality than I've seen in print where the author was actually paid to write it.
If you want me to go more in depth to critique, I will, but really it would feel like really nit-picking at that point.

Kudos

A choose your own adventure. Good idea. Maybe go 2-3 thousand words per chapter, and knock out a bit of that whitespace to make it a little less distracting to read, but there's potential here.

I'm going to offer what I think is a constructive review here. You have a lot of ideas, and that's really what is at the core of being a writer. That, and being persistent. One final key to being a good writer is being open to improvement.  The only way to improve is for you to discover what could be improved in your writing. So here goes:

Check over your story for context and proper wording. For example "I just took a deep breathe and started climbing my sisters foot."  Would be more properly handled thusly. "I just took a deep breath and started climbing my sister's foot."

You are firing off your story in short bursts, with skips and jumps. If you read a well constructed story, you should be able to imagine it as a movie or TV show.  Yours reads like one of those flip-books kids make, where you draw a bunch of similar pictures and flip them fast to simulate motion.

Try an experiment, and see if you can see a difference - re-write this but for every sentence you have here now - write two. And do not advance the plot any more than you have in this little chapter here.

Then, repeat that process a few times, and before you know it, this chapter will be a few thousand words longer than it is now, with a fuller feel, and one that doesn't feel like we're being rushed.

To use a sports analogy, reading your stories is like paying to go see a football game but then only being shown a 2 minute highlight reel when we wanted 2 hours of football.

I hope this helps.

Yeah, need to clean this up a lot