The longer I let a class sit and goof off, the harder it is to get them to act like a class and not a party. I have to get right in there and get them settled or all is lost. Students who absolutely, positively need something right at the start of the period get in the way of this process. Whatever they need can wait.
I told the girl "not right now", and I tried to get the class's attention. The girl argued with me, the upshot being that I wanted her to wait until I had the class under control. I got the class's attention, and the girl walked out the door.
Huge mistake. That is my one major pet peeve. Students do not leave the classroom without my permission.
When the girl came back she claimed that I had given her permission to use the restroom. Um, no, I hadn't. She took a non-response to a question as tacit permission. So, she just left.
I had other problems with this group. I had two boys who could not sit down. They were either throwing things, dancing, or battling each other with rulers. Plus most of the class would not do the assignment.
So, I meant to write the girl up, but I never got around to doing it. She needed to be thrown out. It was just so crazy that I didn't get the time.