Rick,

If she married in 1921, and her husband was already a citizen (by birth or by naturalization) than she automatically became a citizen.  She would not have had her own naturalization papers.

That law changed in 1922.

Interestingly, if a woman who was an American citizen married a man who was not a citizen than she lost her American citizenship.  This happened to my husband's gm in 1913, and she eventually petitioned to regain her citizenship. She was born in Manhattan.

Also, regarding manifests, see https://stevemorse.org/ for links to databases of manifests of various ports, including Baltimore.

Note that passenger's names sometimes are spelled differently in the index of different company's databases, i.e. I have seen (more than once) the name of a specific passenger spelled differently on the EIDB vs FamilySearch.  If you don't find the person when searching it pays to do a soundex search.

Regards,

Sherri Bobish