You know that we are kindred spirits regarding our thoughts on Booth and Ella Starr. I have always thought she was the one "constant" female in his life at this point - despite the separation that went on not long before the assassination. Other than maybe Isabel Sumner, I don't think he had genuine feelings for any other female besides family -- and that includes Lucy.
We can only speculate, but I would like to think that he spent the night with Ella. On this point, I guess I am a romantic... And, one day, I will torture a certain author until he tells me what her married name was and what happened after she went back to Baltimore!