Most of those really intense and "real" dreams happen because during deep sleep your mind accesses emotional memories with brutal clarity, without the critical filters you have during the day - so yeah, your brain is definitely working, but other people respond like it's just cold processing when it's actually something way more emotional than that. What matters isn't whether it was a literal "message" or not, but that this dream left you with some peace, and that has value on its own - your grandmother would definitely be thrilled to know that it calmed you down, even if it's just from the neurology side of things.