Idk what to do

My 8 year old sister says she gets a stomach ache and then she feels nauseous and then she vomits. It’s happens every year like 4 times a year but it usually coz she ate mixed stuff or something bad. She vomits it out and then gets better and doesn’t think about it. But this past week she vomited but she still feels anxious to eat coz she is anxious she might vomit. I think she has anxiety and might be anxious of vomiting but idk she isn’t the type to pull out stuff like this she is really quiet and sensible girl that keeps to herself. This is really bad because is missing out on school. Idk what to do what do you guys think