This can also mean "No, she's fine" after responding to a question about whether or not a female is hurt or in trouble of some sort.
like TehVanarch and Abstract_thunder said, "cô ấy không có gì" would more likely be used as "she's fine" than than the transliteral "she has nothing".
In Vietnamese, "cô ấy không có gì" means "she has nothing". Another meaning of "Không có gì" is "No problem". For example, when you say to me: "Thank you", I will response: "Không có gì". This meaning is always used by the speaker.