This type of event is so common we have a term for it. It's a visitation dream. It can happen at other times long after a person's passing, but it is so common to be just as you described. In fact, I've heard of multiple family members having the same dream, waking up and noting the time, and comparing notes only to find it had been around the same time as one another and that the time was close to if not the same time as the person had passed.
It's good that it brings you comfort and that you have that memory of her. She was paying you a visit for just that reason.
