Daughter facing disciplinary over social media post

[user89066511]

My daughter works in retail in a supermarket. During lockdown at the beginning of the year someone posted on her timeline asking how she was and saying how rubbish the year was. She replied life is pretty normal for me working in supermarket but the customers are more annoying than ever.
Someone has reported the post and she now faces disciplinary action. Can anyone give any advice? She thinks that the company are been unreasonable but I know some companies are very strict on social media posts.

It misses the point to say employees should be allowed to vent if they've had a bad day.

There are formal escalation paths that are there for staff to highlight valid concerns if customers are being rude, obnoxious, having a go etc. It doesn't solve anything by ranting about them on Facebook or Twitter. It just makes the employee 100% in the wrong, no matter how people say "it's so unfair".

...but the customers are more annoying than ever.

It's hardly a rant, though, is it?