Booth's mistress, Ella Starr, and other "unknown" Booth ladies!

[Steve]

The Etta letter is two different letters and was incorrectly combined in Evidence! (I don't know if they were incorrectly combined by investigators at the time.)

Evidence has this at the start of the letter:

New York
April 13

Dear Wilkes,

I received your letter of the 12th (stating you would be in this city on the 16th inst.) this morning and hasten to answer it. On account of a misunderstanding between my landlady and your humble servant, I have been obliged to leave her hospitable mansion and am now (for the time being) stopping at the New York Hotel, after your arrival should you not approve of my present location, it can easily be changed to suit your convenience.

before going into:

Yes Dear, I can heartily sympathize with you...

at the start of the 2 images you found signed Etta (top of the letter). Etta's letter says

"so will I in you and Wllkes have said vengenance is mine."

That seems to imply Wilkes is someone different than who Etta is writing to. The last line in the postscript

Ahem!!! Sam

would seem to indicate that Sam is the name of the person Etta is writing to.