How do you suppose one would address a senior Cardassian lady who is not a military officer but a superior or boss in a work place? Ma`am? Madam? Sir?
We never saw that on the show, I'm afraid. I'm sure some form of respect would be shown, but I don't know in what form.
"Yes, Gul/Legate/Glinn." (delete where applicable) Otherwise they might be addressed as 'senior' or even 'veritable one'. Unfortunately for us, the finer forms of Cardassian social etiquette did not make a significant impact on DS9. For some reason...
I wonder if Mrs, ms, mr exists. Garak was Mr. Garak to some but that is a typical human way used by humans.
I could see there being some form of honorific used in Cardassian culture, the way the Japanese use "-san", "-sama", "-sensei" etc, with different honorifics for different classes, stations, levels of authority, etc. Considering that the Archon in "Tribunal" was referred to as "Madame Archon", (did I remember that correctly, or did I make that up in my head?) I would think that ma'am and sir wouldn't be too far of a stretch as a reasonable extrapolation.
I always imagined something similar to the tú/Usted distinction, except more complicated. But there are soooooooooooo many linguistic options available to convey formality or the lack thereof that you have tons of options.
There are also several Cardassian language dictionaries online, each of them created by a different person for a different purpose. You could try drawing from them, as well. This is the oldest and most comprehensive one I've found (though there are several others out there): http://galileoace.com/Cardassian/language.htm
None of those languages are canon, though. All of us who have designed one have done it off of the very, VERY limited sample of words that were heard on the show. We pretty much had free rein to do what we wanted.
Sir, madame, etc are so human. So white human while we're at it. I'd hope they go for something different.
If you're not sure which human way would be appropriate, or don't like any, you can always make something up and create a Cardassian word that wouldn't translate to Federation Standard at all. Since we know so little of Cardassian language, aside from a few words, your possibilities are almost limitless.