I've heard similar stories about almost every line I have that ended up in that area, but I've never found anything to prove it. I have serious doubts that it's true, although you could have one of your male descendants of Jeremiah Valentine Lamm tested and they could tell you if there is any percent of Native American in the line. I think the "story" behind it is much, much more prevalent in those families who ever lived in Pocahontas County... but my grandmother never told me anything about any of the Lamm family being descended from Native Americans. I have always been told that the Lamm family came over from Scotland, but I don't even know if that's ever been proved, but it's what my grandmother was told by her parents, and so on.
FYI, I have Lydia's middle name as Margaret.