sister's duty?

In “Streetcar Named Desire” I notice that Blance is bossy sister and wanted Stella to listen to her and not to her husband, Stanley. Although she is shown as a sister who is bossy and try to control her little sister, I sometimes felt that what Blance is doing is only for the good of Stella. As an older sister myself, sometimes I tried to protect my sister from getting hurt. Same as Blance who thought that Stella’s husband, Stanley, is hurting her and he does not respect her as his wife. But one thing that escapes Blance advice is that she forgets that Stella loves that man (her husband) and Stanley also loves her dearly but the way he shows his love is different. That is why I think that Blance decision to advice her little sister about her marriage is because she loves her dearly and she does not want Stella to get hurt.