Also just an FYI, no company can force you to come in if you are calling out ill (regardless of if you are or not) It is the managers job to either call someone in or cover the shift themselves. Sounds like she was just trying to be a bully because of your age.

I'm a former manager for a not "fast food" sandwich shop. Our company policy (franchise owner policy, not parent company policy)was to send not only an email, but a text to the employees at our store updating information if there is a change in management. Your manager was at fault. If she did not get confirmation of all employees receiving the email with updates (hence the reason for texting) then it is her responsibility to make sure all employees have her contact info. Especially if they provide a work app that states it is for clock in/out & messaging co-workers/managers, then it is her job to check that app to ensure she had no messages.

This is not a YOU problem, this is a management/company problem.