when can a widow get her own benefits that she earned through work?
They can switch to their own retirement benefit as early as age 62. This assumes you are eligible for retirement benefits and your retirement rate is higher than your rate as a widow
can the widow get monthly benefits if she is caring for the dead guy's daughter?
A widow any age who is caring for the deceased's child who is under age 16 or disabled and receiving benefits on their record  can be eligible under certain circumstances.