Is she underweight? I suspect not. In which case, offer her food at the usual times - no snacking between meals - and if she refuses to eat, then she gets nothing. Next mealtime with luck she will be more hungry, and thus more likely to eat, though still may refuse, so she still may get nothing.
Important: encourage sufficient fluids, especially water, to avoid dehydration. If she is eating no food at all, try making milk shakes using fresh fruit for flavouring and/or fruit smoothies.
It may help you to keep a note of what food she does eat - even if it's just a spoonfull. If she does not eat ANYTHING for a period of 48 hours, consult a Doctor. However, my guess is that within 48 hours she will eat something, even if it's just a bread stick.
Try to avoid giving her sugary snacks, like biscuits, also avoid things like crisps. Try and get her to eat the regular family meals you are preparing. Hide/remove all snack products from the house, so she (or any siblings) can't go raiding for snacks between meals.
In my experience, children rarely stave, though they do go through periods when they don't eat much. If you get concerned that she is losing weight, and/or no food is going in for a period of 48 hours or more, then consult a Doctor to check that there is no medical reason why she won't eat.
If she refuses fluids, then consult a doctor with some urgency.