Grippo's Potato Chip Company review: Union members rights

On 01/31/20, Employer told employee
not to clock in because she longer has a job,
Without giving her reason why. grievance was file. Hearing was on 02/12/20 she find out company fire her
Because she said f**k you to another employee. Company investigation was unfair
Even at hearing they refuse to hear her side and then kick her and the union rep out of the meeting was over. Union is fighting back saying that even if she did say it, she shouldn't
Been fire. My question is why isn't the union charging the company for wrongful termination plus the union has proof the company did a unfair investigation. Why isn't the union using these issues?