My female zebra finch died. Should I get another?

Question
I have had 2 zebra finches (a male & a female) for about 5 months now. I got them from a family friend whose finches had babies, so they were brother & sister. They were always really chirpy and happy and jumping/flying all over their cage. I noticed about a week ago that Frik (the female) started chewing on/biting at the bars of the cage, but shooed her away from the bars & didn't think anything of it. Her brother Frak started doing it a little bit too, but not as bad. I don't know what happened, but when I looked in the cage this afternoon, the female was laying on the bottom of the cage with her head eerily turned backwards. I'm completely lost as to what happened & now Frak looks lonely sitting in the nest chirping pitifully & looking around like he's looking for Frik. Should I get another female? Or even just a male as a friendly companion for him?

Answer
I would get a new immediately and completely sterilize the old one just to make sure that there isn't something on the cage. I've never heard of a finch chewing on the bars unless there was something that could be used as nesting material on the other side. I'm assuming the female died. She may have hit the bars and injured her head (unfortunately, I have had birds hit the cage bars and kill themselves). I would definitely move him into a new cage and get him a girl. Having a mate will take his mind off of his sister. But you will have to watch the two carefully to make sure they don't start fighting.