This story dates back to 1956 and has to be classified as a legend. While the legend may be true, the unusual nature of the event makes it difficult to verify.
Margaret McGrew was involved with launch support scheduling of Eastern Test Range resources, a job contracted to RCA Corporation in the early days of Cape operations. To be an effective manager of this operation, Margaret had to understand the missile capabilities and Range equipment operations. She was a highly educated physicist and also described as a life-long "missile buff" who was directly involved with the missiles being tested on the Range. One such missile under development at the time was the surface-to-air Bomarc. Before Margaret died of cancer on 10 January 1956 at the early age of 46, she reportedly requested unnamed colleagues to fly her ashes in a missile. Bomarc "A" model, airframe 623-13, Air Force designation 54-3053, was launched from Launch Complex 4 on 2 February 1956, carrying ashes of Margaret McGrew. Range records indicate that the flight of the described Bomarc was terminated prematurely by internal fail-safe devices. Of course, official records make no mention of human remains aboard that Bomarc. There is also no monument nor marker to commemorate the event.
The legend of Margaret McGrew has been mentioned by several authors, among them the late Martin Caidin of Cape Canaveral. The most complete rendition of the legend is found in "Women in Space: Following Valentina" by David J. Shayler and Ian Moule, from which some of the above story was extracted.