Why do places of business always put complete ass holes in positions of authority??

My boss is so hostile all of the time. I’m 19 and I work in retail. I was closing alone last night so I wanted to start cleaning up the store. Another cashier had TWO people in Line. So I asked if she could handle it she said yes so I put my “closed” sign up and proceeded to leave. My boss stopped me and told me rudely to head back to my register now. So I explained to her where I was going and she told me she doesn’t care. So I went back to my register helped the one person in line and left. She then called me to the office later to sign a write up that stated that I refused to do my job and willingly help a customer. I told her that I didn’t want to argue but if it’s ok I’d like to wait until the big boss came in to talk to him about the misleading write up she gave me. She said “that’s fine” and then put it in the drawer and told me to go home. After I clocked out I figured I’d just sign the write up since she was sending me home anyways. So I skied to sign it and when she gave it to me she’d written on the bottom “refused to sign write up”

That actually is when I got really pissed off. After exaggerating the write up she had the nerve to make it seem like I refused to sign it. At this point I lost my cool and told her that she’s a liar. And that if it was mandatory that I sign it she could’ve just told me that rather than telling me it’s ok that I wait. So I signed it and today I went in for my scheduled shift to tell her I quit. Just curious if I handled this the wrong way??