My girlfriend is experiencing vomiting, nausea (severity: moderate) , diarrhea, tender abdomen, abdominal discomfort and kidney cyst.

Maybe lots of things: ...like infection, inflammation, malabsorption, maldigestion, dysmotility, more. If she has ongoing distress (as you describe), its time to find out why and what treatment options exist. This may have nothing to do with the GI tract. Untreated urinary tract infection can cause her symptoms too.

ER-now: Cannot be diagnosed online: I suggest immediate ER evaluation and testing.

Medical Evaluation: If she has abdominal pain with abdominal tenderness - medical evaluation can help to rule out any causes that might require surgery.

Emergency exam: Your girlfriend needs to be taken to an emergency room or urgent care clinic immediately! Call an ambulance if you can't get her to a treatment center quickly. A complete exam and more history is needed. She must be seen immediately in a medical center because the underlying causes of these problems could be life threatening.