Dower rights

What's entailed in dower rights in Alabama? I understand the basics: the wife was entitled to roughly 1/3 of the estate of the husband in case he dies, or if she gets a better deal in the will then she can take that. That's easy enough to understand, but when does the wife have to sign away her dower rights? I've just been told that she only had to sign away her dower rights if she inherited the land from her father. If true, that means Sarah's father died in Alabama, or at least had claims to land in Alabama. I have a feeling that's not true, but I'm going to be doing research on the land that she signs away and see if there's another link to William and Sarah. How funny would it be to find a link to her parents but no link to William and Sarah, especially considering that there's a big debate about what Sarsh's last name is. If the new news about dower rights is true, then Sarah's family has been in Alabama for a long time, perhaps even before it was the Mississippi territory. Looks like more probate work for me!