One possible solution to this that I can think of would be that Nellie was writing about Sim and Pearl's daughter Josephine who may have also been called Ortha, and that Nellie was talking about her death, though she died between 1916-1918 (I have never been able to find her birth date). Or there was another woman/child.
Oh, the mysteries! I am continuing to research this and will post if I find anything to update. Below is the note I found.
Written by Nellie Griffin
May 16, 1920
Oklahoma City Okla
301 E. 4 St
Budded on earth to bloom in heaven.
On Thursday morning about seven o’clock as time had past –
into another day – death come into our midst and took from the home of Mr and
Mrs Sim Griffin there (sic) little girl Ortha.
She was a sweet little girl, only nine months and twenty eight days
old. Died 31 day of January. Had been a short life and if the wishes of
friends could have been granted, her suffering days would have been made less.
We will miss the little Ortha as the days pass by. Often will we think of you our Little
Darling and now since you have been gone from us for ever it will seem more joy
than ever to see your sweet little face again.
But God has seen fit to shorten your days and take you to
his home above where there is all joy, peace and love.
So all we can do now is to bow in submission to his will and
be prepared when time comes to cross the Dark River of Death
(the rest of the page is missing)