Stop Disrespecting My Disrespecting!

(I am a manager. I run a team of volunteer workers together with my co-manager, who is male (I am female). We have a strong team who usually supports us through-and-through, and we love working with them, however, one of the new volunteers has taken a disliking to me, constantly second-guessing me, and is refusing to follow my instructions unless my male co-manager has repeated them to her. This eventually becomes too much for me to handle, since I have to fight to make her do anything without my co-manager telling her I indeed have the authority to tell her what to do. One day, I take her aside.)

Me: “Look, [Volunteer], I wanted to meet with you today to discuss our working relationship. It feels to me as you don’t have as much respect for me as a boss as you have for [Co-Manager], and it’s starting to trouble me quite a bit. I wanted to see if you agree with me that there is a problem and if you, in that case, have any ideas of how we best should solve the issue. Maybe I’ve done something that offended you – in that case, I would like to apologize.”

Volunteer: “What? Why the h*** are you calling me disrespectful? That is SO not true. This is ridiculous. Where is this even coming from?”

Me: “Well, it’s been going on for months. I’ve noticed these things…” *pointing to the different situations where she has treated me as I’m not her boss*

Volunteer: “This is bull-s***. That never happened. And if it did, it probably has to do with you being overly emotional and being incapable of handling constructive criticism.”

Me: “Well, we can take it from there. Could you please give me an example of where and when I’ve been too emotional?”

Volunteer: “No! I want to talk with [Co-Manager]!”

Me: “I can assure you that he supports me fully in this. We have discussed it several times. Other members of the team have also wondered about our relationship. It’s affecting our work.”

Volunteer: *yelling* “I DON’T HAVE TO SIT HERE AND TAKE THIS! I WANT TO TALK TO EVERYONE IN THE TEAM, NOW!”

(Said and done. We arrange a meeting with the staff and try to work past the problem. Every volunteer vouches for me, saying that they don’t understand why she’s behaving this way, and asking her to give an example of when I behaved like a bad manager. She gets more and more irate by the second.)

Volunteer: “This is complete bull-s***. My problem with [My Name] is that she can’t handle constructive criticism. She gets all defensive. I can’t work with someone like that.”

Volunteer #2: “With all due respect, simply saying that someone can’t handle criticism isn’t actually criticism. It’s just nonsense if you can’t back it up with something. You’re being irrational. [My Name] is committed to her work and a great manager.”

Volunteer: “I CAN’T HANDLE THIS! [MY NAME] IS SO UNPROFESSIONAL! I QUIT!”

(We were glad to let her go, but she stills swings by and tries to talk to my boss as well as our clients about how unsuitable I am as a manager. No one knows what her problem is.)