Job dilemma and office drama

[wrigley]

My friend's mom has been in the banking industry, ie branch type stuff for over 20yrs. She has no degree and worked her way up starting as a teller. She's always gotten good reviews and never rocked the boat. She has worked at bank A for a total of 9yrs(left after 5yrs on good terms and came back and how now been there for 2yrs.) Her present title is as a Assistant Branch Manager.
Let's call her "Mary".

This past May, HR person who places branch managers *I'm sorry I forgot the proper title*put in a branch manager who was completely wrong for the job. Mary starts receiving complaints from the rest of the staff within the first few weeks of new manager's arrival. Following proper procedure, Mary kept HR person informed of the staff complaints. HR person and Mary had been good friends before placement of drama boss.

The additional red flags that fbrought to HR person included the following behaviour her boss. The boss was constantly fielding personal calls and emails from her family and the man she was having an affair with, keeping her door constantly closed ,never doing her job, treating the staff like crap, and dressing inappropriately for work. Originally Mary shared the office with drama boss but ended up having to get desk outside so she could get some work done and get out of drama boss's path. Nothing had been done by HR about removing drama boss for 6 months.

Flash forward to a baby shower that happened 2weeks ago for a staff member of the bank. The party happened off of company property and it was a non company event. Well someone starts to trash talk about the boss. Mary puts her two cents in too about the toxic workplace, she specifically said was that she didn't agree with drama boss being involved in a interacial affair.
I don't what was said but I doubt it was pretty.

Unbeknownst to Mary, the rest of the staff is emailing back and forth with in the bank about what was said during the party along with her comments. Heads start to roll. Mary's boss was fired this past Tuesday for failure to do her job. HR person asks Mary if she made comments at the party. Mary says yes because Mary is honest and good friends with HR person. HR person tells her that they are having a meeting this Wednesday about everything that is going on and she is being written up for her racist comment. Those who wrote the original emails were just told that they can no longer email non business issues on company time. Mary is concerned if and when she tries to get another job that this incident will haunt her whether she signs the written warning or not. Keep in mind HR person's boss also is aware of what's been going on at this branch.

I have no clue about the corporate culture. I agree that Mary should not have said in front of her staff. All I could think of to suggest is to get a hold of a lawyer for advice because she doesnt think she should be held accountable for something that was said out of the workplace. I'd appreciate any comments.