My wife hates been called “luv” mainly old dudes that think they are been nice, so she calls them luv back. Maybe someone needs to be greated every morning with with a nice big smile and a good morning flower.
Also if the getting left on your own for a smoke break when busy happens, just go for a smoke break with her, or be on your phone and say something like “I don’t know where Sarah went she just disappeared, oh wait I’ve found her outside having a smoke break, do you want me to tell her to come back inside”
As it’s a uni job it’s now your mission to wind her up as much as possible, don’t worry about bad references or CV gaps if anything goes wrong.
Also look up constructive dismissal
What is it about a smart phone that you don’t want/like?