This is confusing to me. While "She is a weak journalist" makes sense, it is a strange sentence.
It would be more appropriate to say, "She is a poor journalist."
However, I thought слабки meant physically weak and if so then this sentence is certainly confusing.
Слабкий could mean a variety of things, not only physically weak. I'd say that your translation is better here, but it may really depend on context.
Both the suggested translation ("she is a weak journalist") and Crookfingerjake's alternative ("she is a poor journalist") sound natural but ambiguous to me.
I don't understand the variety of meanings of "слабкий", but if it can mean both "physically weak" and "bad", then maybe "weak" is a better translation than "poor" because it preserves the ambiguity (unless "слабкий" can also mean "lacking wealth").