I am a 15-year-old female, and I am currently a high soprano. I can currently sing from a low C4 to a high F above the bar. Is there a way I could get higher and become a coloratura soprano or gain an octave?
You already have a full soprano range: C4 to F6. Coloratura is a vocal quality, not a range. Coloratura voices generally have a light quality to them, as opposed to the more powerful voice of a dramatic soprano. Coloraturas specialize in highly decorative passages with lots of runs, trills, and other ornaments.
So coloratura is a skill to develop if you have a lighter-sounding voice. At 15 your vocal color may still be changing, but you'll have to wait and see.
Also of interest...
You dont just simply add a octave. Most singers range is between an octave and maybe a 10th. Even then a 10th is extraordinary.
Singing around middle C is hard for soprano and very few ever get to the fabled nessum dorma high B.
Your range will gravitate between the E above middle C to the G a tenth above it. That is fine. You will have to become pretty great before any more is required.
Colatura as a style is not dependant on any particular range for the soprano at least. It is more to do with a style that is rich in ornamentation. This makes it very demanding to the singer and only the really great female singers ever excel at it.
Dame June Sutherland probably being the greatest singer of this type in 20th century.