Hello. Orange vomit contents, though unusual, are not as worrisome as bright red, maroon, tarry black, or dark pea-green contents. Did she eat anything yellow, orange, or red in the prior 12 hours? Any fever at/above 101 degrees Fahrenheit? Any stomach ache? Any diarrhea? Is she still urinating at least twice daily? Is she still eating/drinking normally since the one vomiting episode?
Does she have any chronic health problems or long-term medications?
You appear to be offline, so I will leave some general medical advice.
If she ate or drank anything yellow/orange/red in the past 12 hours, that might be the source of the orange color. Seek medical evaluation for: fever 38 degrees Celsius or higher beyond 4 days OR at/above 40 degrees Celsius; stomach ache that lasts beyond 2 days or is severe; diarrhea that lasts beyond 7 days or includes blood or mucus; poor food/liquid intake, especially if not urinating at least once every 8-12 hours in a teenager; vomiting more than 3 times in 24 hours OR which lasts beyond 2 days.
Also, seek medical evaluation for bright red, maroon, tarry black, or dark pea-green vomit contents.