She worked all the way through middle school, high school, college, and veterinary school. Now she works
four ten hr shifts at a veterinary clinic as a doctor of veterinary medicine. What does she want to do with her days off ? Wait tables!!! I think she might be addicted to our pizza ! LUCKY US!!! 
Some people just enjoy the insanity of working at a restaurant.
Or she loves the easy extra money to help pay off her school bills 
either way it’s a win win
For over a decade I waited tables all the while moving through a bunch of full-time jobs…I enjoyed being a waiter and the money I made…It gets in your blood…
A wait staff person does make pretty dang good money. My wife had to waitress for a girl that came in last night with no voice. The girl hosted instead. My wife rolled in $176. Not real sure how that rates with some of your places. And there were 2 other persons on the floor waiting tables.
Goes to show that some people just have fun doing what they do. I would feel ultra blessed having a person like you have wanting to come back time and time again. Should make you feel good!!