Thank you for the query.
Likely that the abdominal pain
and vomiting is side effect of medications she is taking for her headache.
Can take some medications like liquid paraffin
to relieve her constipation which is available over the counter. Mild antiemetics like domperidone
if available over the counter can be taken to reduce vomiting and nausea.
If symptoms are severe or not improving worthwhile seeing a gastroenterologist.