You might check the Hartford Mark Twain House. If memory serves, they have
an old "home movie" showing Nina graduating from college with her mother
around. That might be at Elmira, now that I think about it. It has been
years since I saw it.

You might look at obits for Nina. If memory serves, there were some with
information you don't normally find about her in the reference books. Again,
it's been years, so don't quote me.