in english the second indefinite article is not necessary. to say, 'he has a belt and shirt' is perfectly acceptable
Why in the beginning was apel was either apple or apples but here kemeja cant be shirts? "She has a belt and shirts"?
Just a guess: while it could mean that and be correct grammatically, I think we have to learn a bit about the context subtleties. From what I've seen, the language is not always very specific so context matters a lot. Depending on context, this would mean she is wearing a belt and shirt ( ;) ) or she has multiple belts and shirts (in a store or at home or whatever). Anything other than that might require more specificity in the language (she has only one belt but more shirts, she has only one shirt but more belts etc), so you would use numerals or plural forms for that. But it's just my wild guess.