How do I answer this interview question?

You might remember I was fired from my last job. Basically I told my boss to go to hell. Although the following details would never come up in an interview, allow me to give you the background:

I found a lump in my right breast on a Saturday. First thing Monday morning I called my doctor. They had a cancellation that day and could see me at noon, or I would have to wait 3 weeks. Of course I chose that day and I called my boss (owner) and asked her to keep my business private, but I was calling in.
My boss was not supportive. She told me I was neglecting my job (I already had 82 hours on the clock in a commission only role and I ranked #3 out of 8 in sales numbers). She told me that in order to call in sick I actually needed to be sick, otherwise I needed to plan doctor appointments on my own time. I told her I was scared and my health was most important to me, and I was not coming to work.
So I had a mammogram and an ultrasound that day, confirming a solid mass and a liquid cyst. I was scheduled for a biopsy the following Monday.
Long story shorter, I got someone to cover my shift. My boss came in as I was writing it in and crossed my name off of the previous Monday, writing “personal day” on it and the upcoming Monday. She was being openly hostile to me, for reasons I don’t understand.
So I went and had a biopsy. GOOD NEWS it was benign. Yay!
So the following week my boss called a staff meeting, where about 15 people were in attendance. In the meeting she called me out, saying to the whole staff that we “cannot just come and go as we please” and “if you call in sick you must be sick.” Then she looks at me, again in front of everyone, and goes “Is that alright with you, GloPro?”
Beyond unprofessional and immature, in my opinion. I kept my mouth shut the entire meeting and when it was over went to talk to the Director of Operations about how angry and embarrassed I was that the boas shared my business with everyone, inaccurately, and scolded me under false accusations. My boss butts in, and I gave her a piece of my mind. Then I lost my job.

Sorry for the long story. But my question is, when being interviewed, how do I answer as to why I have no job, and why I left my previous one?