What Causes Nausea And Severe Pain In Abdomen Of A Child?

I have a 6 year old overall healthy child who has dealt with the loss of someone very close, she has refused to eat for 4 days now maybe a little picking at food she is still drinking going potty both pee and poop she complains her stomach hurts and it feels like it's tied in a knot, no fever she did vomit 2 nights ago 1 time just clear she has an appointment tomorrow morning with her pediatrician just hoping to get some relief before her visit to the doctor as i hate seeing my little lady feel this way