I have lots of Rigsby information, but very little of it is after 1900. I'm afraid I can't help you with your grandmother, but when you get one more generation back I will probably be able to help.
I'm currently going through the 1900 and 1910 censuses for Rigsbys, but I haven't gotten to WV yet. Unfortunately, that will be at the very end, so it will be a while. I'll write again when I get there.
I can tell you that in 1880 there were Rigsbys in Berkeley and Pocahontas Cos. They appear to be descended from one of the Wake Co NC branches, but I don't have them fully worked out yet.
Let me know when you find out more about your grandmother, and I will let you know if I turn up anything.
Oh, wait. I just looked through my miscellaneous Rigsby notes, and I may be able to help you now. Did your grandmother marry a Kerr and live in Charleston?