Very nice story. I could feel how everything was moving so fast and making the world so unattractive for Stella, I totally emphasized with her at the end.
My biggest suggestion for improvement is in the dialogue, and the second is a couple of places you tell us little fragmented pieces that need to be expanded or removed completely.
On the dialogue, the phrase that made me fixate on it was, "Were going out for tea to the Hannah’s we’ll be back late we want you all in bed by eleven ok” This piece is confusing and in my opinion needs the most work. My suggestion would be,
Stella's new Foster parents stood at the door wearing nice outfits. "If you need us, we'll be at the Hannah's house, the number is by the phone and also on the refrigerator. We know there's no school tomorrow, but be in bed by eleven, we should be back by then."
This way, you're not just pushing them out the door, you're showing that they are trying to be good parents, but just missed all the signals. You can then continue onto Stella's, "Can I stay at a friends." That line is very believable and works well.
Nextly, “I love you pop” she whispered “and I’ll never forget you. The police will get who did this horrible act and they will suffer hopefully more than you.”
That whole thing sounds like a movie of the week from Lifetime. I didn't feel the love or any sort of integrity in her words. In my opinion, no words could work to say that. I think you could have done better to write; She decided she would hug him, and mouthed, "I love you." but no words came out.
Just suggestions for the dialogue and phrasing, of course. I think your piece is good now, but it'd be excellent if it had more believable dialogue.
Then, onto the scattered descriptions. The main place is on the Luvox, you went way too far into it. I think it would have been more powerful to say; Stella saw on the news that a violent murder had been caused by an uncontrollable side-effect of the new antidepressant Luvox. Luvox sounded familiar, maybe that was what her father was on when he shot her mother. Maybe he wasn't so evil after all.
I like it that way because it's just one more thing that is totally out of Stella's control. However, your way does bring into her helplessness with the police, maybe you could consider revising it to include a little of both.
In the end, I don't nit-pick over grammar and spelling, most of your mistakes didn't detract from the story, but as you know, it needs a thorough going over.
An enjoyable story, and one that will keep me thinking.
