I can see how some situations *broadly similar* to this one might be MYOB - but this is not that situation.
1. Everybody else in the family knows, including this woman's sisters.
2. This lack of connection has affected her relationship with both her parents (here meaning "her mother and her social father" and not meaning "her bio father" who doesn't have a relationship with her at all).
3. She's estranged from her closest relatives, so this news won't negatively affect her relationships with them.
There's no good side to keeping a dead woman's secrets here.
no subject
1. Everybody else in the family knows, including this woman's sisters.
2. This lack of connection has affected her relationship with both her parents (here meaning "her mother and her social father" and not meaning "her bio father" who doesn't have a relationship with her at all).
3. She's estranged from her closest relatives, so this news won't negatively affect her relationships with them.
There's no good side to keeping a dead woman's secrets here.