My daughter was just diagnosed with granuloma annulare. She was prescribed a topical cream. Is this something she'll have the rest of her life?

No crystal ball. It's difficult to predict what will happen with ga; a lot depends on what is causing it, and often the cause is not clear at all. The localized form has a tendency to resolve spontaneously. The generalized form tends to be more persistent. Your daughter should be checked periodically for diabetes, as ga is sometimes a harbinger of the type i form.