The first thing that Shiroi noticed was Satoshi's eyes which were looking directly at her. She had no idea where she was, but judging from his concerned expression, she assumed that something bad might've happened to her. After all, she'd never seen Satoshi react like that upon seeing her before.
Something definitely happened, and she just woke up to it.
Now that she got a better look, she noticed that everyone was actually there. From her parents to Satoshi's parents, and then there was the Nurse and her cousin. Seeing all of them made her panic a little bit since she could tell that something occurred while she was unconscious.
It totally flew out of her mind that she could be the cause of everyone's worries. It was only when she noticed the amount of blankets wrapped around her that she understood what was going on. Her mind instantly replayed to when she tried to activate her superpower, and then she lost consciousness since she was trying too hard at it.
Satoshi got the short end of the stick back then ahah