Donna is experiencing disenfranchised grief. The disenfranchised grief is a term used to describe a grief that has no recognition by society. In this case, Donna's type of mourning is not recognized because she hides the real cause of death and mourning is experienced differently according to the causes of death. It is common for people to hide the fact that a family member commits suicide, this is because there are many stigmas around the topic.
I hope my answer can help you.