I dont want to deter you from voice acting because female voice actors are few on this site. So ill say that I can clearly hear that you are nerves. so im assuming you live with other people.
Ill give you some tips that should help you.
Tell your room mates or parents that you are interested in voice acting. Tell them they might hear weird sounds coming from your room but you are simply auditioning for rolls in cartoons.
You could also make a sign for your door that says (Voice acting in progress) So they dont walk in on you.
Also try singing Karaoke in front of people to get rid of your stage fright. Dont be afraid to be loud or sound dumb. Be silly. Try voices outside of your normal voice.
I hope this is helpful.