"She sees her boss as a father."
Translation:Sie sieht ihren Chef als Vater.
How come no indefinite article? Also if it were there would it be accusative einen? As it is like saying her boss.. As she sees her father.. Could be wrong thinking that
There is no need for the indefinite article in this sentence in German. The sentence sounds perfect without, whereas, if you omit it in English, the sentence sounds odd. So there is a good reason to replace the literal translation ("....als einen Vater") with a more common variant.
It's a question of the case. "Wie ein Vater" would be attributed to the subject, as it's nominative case, like in "She plays the piano like a god", but here it's unlikely that "she" is like a father, but her boss is to her, so it's accusative case: "wie einen Vater".
der Chef is singular masculine, and the ending possessive pronoun is matched to the word it refers to, in gender, number and also in the case, which is accusative here (like most direct objects), while "ihr" would be nominative case, singular masculine. A correct sentence (not a direct translation, though), would be "Ihr Chef ist wie ein Vater für sie" (nominative case here, as the boss is the subject).