my nonverbal little sister got her first period

my sister is 10 years old, and her periods started this morning unexpectedly. she doesn't talk and doesn't understand most things, only if she wants to understand it. i know for sure she won't understand periods and how to manage them, how to manage period underwear or pads. what can me and our mom do in that situation? very lost and anxious. plus she's going to school with assistants, but they never go with her to the washroom or anything, they're there only for supervision and help in class. she also seems confused and scared.