does the fear of acting dissappear after a while?

Yeah, being in theatre may seem terrifying at first, but pretty soon you become more relaxed and the fear starts to go away. It took me several plays and a couple years before I was completely comfortable on stage! Every actor learns at their own pace, don't worry if you're still scared after awhile. Even the pros can get stage-fright once in awhile! You may feel scared still after several plays, but this type of fear is more excitement, like butterflies. Soon you'll learn what to expect and be more confident in your art!

As with having a friend with you to start is a great idea! You can support each other. In my first play I didn't know anyone, but you make friends quickly, it's just like making friends anywhere else, and here there's people with a similar interest in the performing arts! 
School is a good place to start, although I've found that theatre courses outside of school (in the summer maybe?) help you tone acting skills more. Whichever place you'd like to start is fine. If you have aspirations to be a famous actress, good for you! Ambition helps a lot in theatre! And remember, don't expect to learn everything too soon, the learning process is a lifelong thing, that is, there's always something new to find! Have fun in your first theatre production, and as all awesome actors say, break a leg!