See my earlier post. I still do not know what happened to Lucy. I wrote to Juab Co., UT about records for the Watts but received no reply. I have not found the names of the Watts children who died in the 1880's. If you go to The Watts Hays Letters www.wattshaysletters.com
there is considerable information about the Watts and in "The Families" section there is a link to a genealogy file which includes the families of Clara Alice Richmond and John H. Watts. Dewitt is mentioned in many letters, John and Alice are mentioned in a few of the After 1872 letters. Dewitt's wife is not mentioned nor is his marriage.
I don't know for sure that Lucy's last name was Howard but there was an Alice Howard living with the Watts in 1880 and John's middle name was Howard so it is likely.
On the later Censuses Clara Alice always list's her mother's birthplace as England. John lists his mother as born in Utah.
Hope this helps.