I think the apparition is believed to have taken place around the year of 40 AD. Now, I’ve heard two traditions regarding Mary’s age, one that she lived until she was 63 years old and the other that she died eleven years after Jesus. That sets her life span to 18 BC-45 AD, if Jesus was born in year 1 BC.
I believe this apparition took place shortly after Mary’s assumption. I don’t think it’s possible she could have made an apparition while still living her earthly life.