The causes of why a beardie would stop eating is so varied, ranging from needing a new uvb light to impaction (eggs if it is a female or from eating substrate). Parasites also can cause lack of appetite. New caretakers don't really stress out a l hungry reptile much... If they are hungry, and their husbandry remained the same, they don't mind who feeds them. When a live prey item does not even trigger any response, that is a red flag that something is wrong. They may be picky about salads but beardies love live feeders. I would suggest that the owner double check the tank's basking temp, cool temp, how old and what type of uvb is he or she using, what type of veggies were used, eliminate all loose substrate from the tank, bathe the lizard to see if it has not pooped for days, what supplements were used, if it is a female, is there an area prepared for her to lay when needed.