Ah now this is my forte, ive run dream workshops and had articles on dreams published, not bragging just saying you can trust what I say - make your own mind up though if you know what I mean
When you have a re-occuring dream, its basically your subconscious mind wanting you to take notice of something important that needs to be dealt with - usually an emotion your burying, a situation your ignoring, that kind of thing.
Also, people in our dreams dont always represent the person we are dreaming of, but rather a part of ourselves that is symbolised by that person - ie your nan could represent the part of yourself that is wise, or experienced, or however it is that you see your nan.
No-one can interpret dreams for you, anyone who says they can is a charlatan, simply because every symbol and/or person in a dream can only represent what it means to your mind.
So what you need to do is have a think about what your nan represents to you, what parts of her personality or experience do you relate to, and then figure out of if there is anything going on in your life that could be represented by the situation/story of the dream either literally or hypothetically.
It should become a bit clearer then.
And rest assured a re-occuring dream does not mean it will come true, its an old myth but a myth all the same
Hope that helps, feel free to PM me if you want to talk about it in more detail
