Sudden onset of abdominal pain
in children is most likely to be Appendicitis
, if location is right lower abdomen. This condition is usually associated with vomiting and child refuses to eat n drink too.
However diagnosis can be confirmed by USG and clinical examination.
First attack of appendicitis is not an indication for it's removal until and unless complications like rupture occurs.
So you need to contact physician soon for diagnosis and treatment.
As well, renal stones
can cause similar symptoms but age of patient will not be too young.
As you are also telling she has not urinated means there are chances of urinary tract infection
. Urine routine and microscopic examination will confirm it.
So even though there are many possibilities of condition; you need to consult doctor
immediately to arrive at right diagnosis.