Posting silly things on facebook and thus endangering your employment........what sort of numpty does that.......................................................  
  
I'll get me coat  
  
Having (just out of interest of course) performed some fairly extensive research into this she's fooked. Usually you have a very good chance of claiming unfair dismissal for social media comments but the fact she's mentioned the company, abused someone and its a private group that's specific to that company I think she's bollox'd. 
  
As a mobile phone provider I would be 99% sure they'll have a social media policy which will class this as gross misconduct.