She is in her normal world where she is home schooled and doesn't get out much.
After 3 years of homeschooling, because of problems in middle school, her parents decided that she will do her senior year at a physical school
So far she has made it 2 days and is on her third day about to go to lunch with her only friend
Everything was going great until a school shooter showed up. Ally helped many people escaped the only person she couldn't save was her best friend Scarlett. She also got hit and was sent to the hospital. She and scarlett were the only ones hurt.
She becomes depressed and doesn't go to school anymore. She gets fed up with being depressed and realizes she wants out of it, but can't do it alone. She calls a teen help line and starts getting better.
She eventually gets better after finding help. She makes enough progress that she is able to get back to school by choice and and live her life almost the same way as before.