Alright. Seeing as how you seem to have been working on this for quite some time, I will do my best to give you the most detailed explanation I can give.
The idea of young (either pre-pubescent, or teenagers from what I gather) spies that are working to seemingly save the world is a concept I have seen performed in two different animated shows, Kim-Possible, and Totally Spies. If I were to say which one I thought of the most when I read this, it would probably be Totally Spies, but as long as you don't start using lip-gloss and pocket mirrors as secret spy gadgets, I can say the only similarity is that they both involve a team of three young spy girls.
I don't know what the stars are from what I have read, and that might be a slight problem. If I don't know why I should be hopeful or concerned about whether or not they get these stars, I will spend most of the episode asking myself questions about what the stars are. Sure you gave some fore-shadowing, and some classic vague backstory talk, but for the most part, even after reading through all of this I still don't really know what the score is. Can these stars bring about the apocalypse? Can they potentially save the world?
If I were to make a suggestion, do the classic pre-show monologue. Explain the basic premise and such, who Rena is, what the stars are, what could happen if they fall into the wrong hands, etc... make it brief yet informative.
You took a little while to get all the names out. Looking at this as a script means I have to pretend to only know what is said or described to be on screen. Sasha was a nameless face in her first scene, and there were opportunities you could have said her name, such as when she called Jade, instead of saying "It's Me" you could have said "It's Sasha". Also, you have them talk to the Alejandro by calling him "Alex" or "Al", which isn't a big deal, I know who they are talking to and who he is, but it might be worth at least mentioning his real name once.
Vision: It's a good idea with a good premise, I can see many different ways it can go, and you did a good job of building it up.
Originality: Other than the other shows I said it reminded me of, the idea of spies going to find secret magical objects in order to save the world isn't an idea I have seen very often.
Technique: Basically what I said up above, you have a good idea to work with and did a good job of building it up, but there are some things you can improve. Some things need to be elaborated on or explained a bit more than they are, like why Annabel already had half of a star sitting on her desk. Also some things don't seem to make sense to me, Annabel picked up the two halves, put them in her pocket, and then took them right back out to put them together. Also the three girls walked up to the building where the footsteps led them, the parents answered, and very clearly said they had two daughters, the girls mentioned the red star, and them mom clearly reacted to it, even saying something that hinted that she knew what it was, I don't see how the girls thought it was possible they were at the wrong house, especially considering that they are spies (fairly important ones it seems).
Impact: How should I put this? Like I said above, I don't know what the stars are or why I should care whether or not they retrieve them, so if I perhaps knew a bit more, it might evoke a bit more emotion in me. The scene with Annabel and her sister was fairly well written, it made me feel sad that a girl possibly just watched her sister get swallowed up by the earth. I think you should make me wonder/worry a bit more though. If I were to make another suggestion, add a scene in between Annabel falling in the hole, and finding out that she is fine, so that I worry that she might be injured or in danger, you went right from her falling to her being safe, so any worry I had for her was short lived. Stretch the worry out, tug on my heartstrings.
Overall, it's good. It shows promise, I could definitely get into the story. Just consider what I said.