But your real question was about Louisa who died at Wheelock. I'll see if I can find anything but I'm guessing you've already looked everywhere I can think to look. You might try the Indian-Pioneer Papers. I don't know how much of them is online. NSU Library has the index on microfilm in their special collections.
I would very much like to read the letter to Louisa, if you don't mind, in whatever format is convenient.
You can email me at martikw@history-sites.com.