Mmh hard one, I heard the same about what you read and my mom also had those dreams, exactly at the moment somebody died. Her grandmother in that case. You should look up precognitive dreams but I donīt know in which extend that will help you since the dream maybe wasnīt really precognitive anymore. Maybe it was tho.

My advice, contact her. Maybe mail her, something discrete to not get her in trouble with her husband. If everything is fine, perfect! I think itīll help you getting peace and maybe itīs a step in the right direction of "finishing" your business. Just my advice. You two were close at one point and in my opinion itīs perfectly fine and normal to worry about somebody who played such a big role in your life..

Hope that helped!