She may be able to nail them for slander but that is everyone's right and has nothing to do with a confidentiality agreement.

I am not a lawyer so take what I write with a pinch of salt.

The remedy or defence for slander or liable is the truth. If what she or you say/write is true, then it is not slander or liable.

You need to look at the specifics of your employment contract. Or get legal advice on it. Confidentiality clauses may or may  not  be generic. Yours could, in fact,  cover clauses which relate to not "trash talking" your employer or fellow employees besides relating to non-disclosure of "propriety information" or information you would know because of your employment. Usually  the only reason you do disclose, is if you are legally compelled to do so. 

My partnership agreement does cover restraints on bad mouthing fellow partners and employees during the course of partnership/employment and after. So you need to check yours for the specif wording. However, if the other side, in this case your employer and in mine, my partners, trash talk me, they breach the agreement. The restraint applies to both sides. If your employer trash talks her employees or former employees, she has breached the agreement and the clauses may become void. Usually, what applies to you, applies to her too.

I would not trash talk her - her own conduct indicates she is trash. No reason for you to do it when it is clear she is her best spokesperson.  

In the UK, my understanding of gagging clauses is where there has been some dispute between employer and employee, which has been settled with a payoff to the employee in return for them not speaking about it at a later date.  However there has been some publicity about these lately (I think also in the USA re: Harvey Weinstein) that these should not be valid where someone has broken the law in a major way.  

I don't think what you describe would be likely to be legally binding at all.  Your employer is just trying it on.  It is in practice, very difficult to prove libel or slander - you have to show that you have lost out financially from it.  

What does the document say? Probably depend a lot on the wording.

I don't know what the actual wording states but in life I can say- don't burn bridges with employers, even the bad ones. Just leave peacefully with proper notice and don't look back. As long as you live your life on the higher ground, let her do what she pleases. Shouting from the rooftops that the owner is a lush won't help you in life and can wind up costing others their livelihood... Just not worth it. 

Also, just want to add - it might be fun to slam her online, or whatever you are hoping to do, but if she takes it to court, you could end up with attorney fees and a lot of heartache, and not necessarily a slam-dunk win, either.  People can sue you for ANYTHING, and make your life difficult in the process.  Even if she loses, you aren't guaranteed to get attorney fees back.

I'd find another way to deal with your anger at her.  She sounds like the type to make you pay for it regardless of what that agreement says.

Courts will not enforce an NDA if the information sought to be protected is not confidential or valuable. Information that is in the public domain or already known by the receiving party is not confidential, and an NDA protecting such information will not be enforced.

Your boss's alcohol abuse is not confidential or valuable information if she's slugging back liquor on a regular basis at her own bar where the public is welcome.

Sounds like she is bullying and intimidating her staff with these NDAs, which would not be enforceable by a court regarding workplace gossip. You should probably take your copy to an attorney in your area to receive the best information. Plenty of business owners have found themselves in legal trouble for trying to use NDAs in this manner.

Regardless of what you signed, I would probably withhold from trash talking your employer in social circles. You never know when a potential future employer might be listening. Bosses tend not to hire people who have a habit of bad mouthing their past bosses, regardless of how true it is.

It will depend upon the wording of the document.  She may well have stipulations in there that are meant to stifle any discussion about anything that happed while the people were at work.

the simplest thing to do in these situations is to not work for jerks and then move on... keep your mouth shut because those who badmouth EX employers are often viewed as problems themselves.. whether they were or not.

Read the details of your agreement, and take it to an attorney if you have questions. I have definitely seen agreements that deal with "reputation."