What Causes Stomach Pain Along With Vomiting Bile?

My daughter threw up one morning and it was yellow, possibly bile, and then was fine the rest of the day and for a few days complained on and off about her stomach hurting. then a few days she got sick again and threw up, yellow stuff again, and again in the morning time. then tonight she complained that her stomach hurt during the day but not enough to make her lay down. hasn t ate very much and then tonight got sick and threw up a little again.