Before sharing the health information about the new cancer therapy with her grandfather, Yolanda should investigate the new therapy in greater detail. This would allow her to understand the therapy's effectiveness, potential side effects, and suitability for her grandfather's specific situation. Once she has gathered more information, she can then decide how to approach the conversation with her grandfather and/or his medical team.
Additionally, discussing the therapy with her grandfather's doctor would also be a wise step, as the doctor can provide professional medical advice and insights tailored to her grandfather's condition. However, the first step of investigating the therapy is crucial to ensure that she has accurate and comprehensive information.