My friend was renting a house here in California. Last night the house and everything in it was destroyed due to an electrical fire that started in the fuse box. It seems that there had been a previous fire, although a small one, prior to my friend renting this home. There were no smoke detectors in the house and she did not have renter's insurance. Where does she stand legally?

She is out all of her property, she walks away with what she can salvage and with a lesson to always have renters insurance.

The owner will hopefully have fire insurance on the actual home, where he will be paid for the loss of the home.
The ower may be fined by the fire inspector if smoke detectors were required by code on that property

IF (and it's a big if) you can prove that the wiring was not repaired properly after the previous fire, she MIGHT have a case against the landlord for negligence. But it's a long shot. She goofed by not having renters insurance. Generally renters insurance is not expensive and more that worth the cost.