I had a dream about my horse last night/two questions...?

IMO your subconscious saw the filly that resembled your mare and wondered if it was by chance that she looked like your mare or if it was some sort of sign. When we loose loved ones in tragic unexpected ways our minds try to cope by providing solutions that ease pain. I would not trade your stud for this filly. Instead, I would work on your stud and let your mind be at peace. God keeps all his creations forever. It might help you bring closure if you did go to see where your mare died. Let yourself mourn. It is sad and you should feel sad. I am sorry for your loss.