Franklin was very good at a hard technique: shooting X-rays through crystals and reading the patterns. Her image known as Photo 51 made it pretty clear that DNA was a helix.
A colleague showed it to Watson and Crick without asking her. They used it, plus her data, to build their model. She got a passing acknowledgment.
She moved on to viruses and did important work there too. She died of cancer at 37, four years before the Nobel went to Watson, Crick and Wilkins.