Me 34m very close friend(35f) of 15 years is ghosting me

We have been friends for 15 years since Uni and when we were younger she helped me though some very tough times. In the last few years contact has dropped more and more as time gone on. However we would still message and meet up once or twice a year. In the last 18 months she basically never replies. We meet up around 9 months ago and she apologised and said she valued our friendship. Since then there has barely any contact and she has not replied to a message for 4 months. She did have a lot going on with family illness and changing job. It’s seems like the friendship is gone. What I am struggling with is the lack of closure. Anyone have any advice ?