Should a County District Attorney be able to ask the federal government to seek the death penalty?

I wrote a book recently (unpublished). In it the District Attorney asked the Federal Government to take jurisdiction over a case in which she was to file charges, and recommend the death penalty. It involved the drug related death of a sixteen year old girl. The question I have is did she have a right to make this request simply because she practiced law in a state that did not offer capital punishment for a crime or does it undermine the right of a given state legislature to write and enforce its own law?