Is it okay for a 14 year old girl to not shave her eyebrows ?

Absolutely fine. I'm sixteen and have only once ever really done any maintenance on my eyebrows, and that was a while ago. I haven't really felt the need to. Honestly, what someone does with their appearance is their business. If they like how they look and feel comfortable with it, then more power to them. They like their eyebrows unshaved? Just fine. Want them shaved? Also fine. It's no different from having a personal preference for your hair-style.

Yes, you should really not shave your eyebrows at any age, try waxing, threading, or tweezing instead. :) At 14, you are still so young and naturally so pretty so you don't have to touch your eyebrows if you don't want to!

Why would you shave your eyebrows in the first place. Never saw a girl with shaved eyebrows.

Sure it's ok, there's nothing wrong with being natural in your appearance. It's what you were born with.