Text Message Breakup

I know they say good help is hard to find. The last few months that has proven true at my bar.
The Sports Bar is a small beer and shot place with a separate dining area for lunch and dinner patrons as well as the late night underage crowd. The bar area has seating as well. All together the dining room consists of 21 tables ranging from 2 to 6 tops. The bar area has 10 tables, and when the weather is nice there is a patio with 8 tables. There are no sections, no rotated seating, and no hostess. On any given shift there is only one server working the floor. This is one of the reasons I applied for a job at the Bar.
I had been working at a place that had no less than 3 servers working at a time. Most nights we were fighting over tables. There were sections that were unfair and assigned (some sections had over 10 tables, including a "party table" seating 20, while some had 5 tables consisting of only 2 and 4 tops) and customers were asked to seat themselves. There were nights when one server would have no tables and another would be in the weeds with their entire section full.
Most servers are coming from places with sections and multiple servers. In fact, I have never been to another place with only one server working the entire floor unless someone called in sick or quit. It can be difficult and overwhelming at first, but when you count your take home at the end of the night you realize it is totally worth it. I have made one third of my rent on a lunch shift, and my entire rent in 2 weekend shifts. I love this aspect of my job.
At the beginning of the summer we fired the only other server the Sports Bar had (yes, there were only two servers). One of the bartenders picked up two of the shifts while we looked for a replacement. We hired 2 new girls about 3 weeks later. I trained both of them on the second half of doubles and their first nights with me were Friday night, our busiest night by far. After training both girls a few times, the first worked her first shift and called to quit the next morning. The second never showed up after training (there is a story on this but I will tell it later). We were able to hire another girl who worked all summer until she went back to school.
After she left we hired two more girls, both part time. One is OK, Katie, the other...
In the middle of the lunch shift I received a text asking if I could work Katie's shift that night. I told her I was sorry I couldn't but gave her the number or the other server and a bartender that sometimes covers serving shifts. As the lunch crowd began to thin out I received another text from Katie. "I hate 2 do this but i can't get no one and its 2 much stress have them mail my check i quit" I replied telling her to call the boss. She sent me another text saying she was not going to call. Great. Now I was left with the unpleasant task of telling the boss that the server that was supposed to be there in 4 hours was not coming in ever again.
Who quits their job by texting a coworker?
I ended up staying at work past the point of making it to class.