Question about using "eine"

I just started learning a couple weeks ago, so apologies if this is a dumb question... the lesson I'm on currently has me typing out what I hear from a prerecorded audio file. The recording says, "Ist sie Schauspielerin" My question is do I not use "eine" after the word "sie"? If not, why? I read it as, "she is actress" and I feel like it needs "eine" so it would read "she is (a) actress. I know that "Schauspieler" (masculine) becomes feminine with "in" at the end. Actor become actress. I don't understand how i'm getting the word/letter (A or an) in the sentence above.