My thanks to Truman Price for his kind assistance in locating the song in the version my sister remembers. It is in the 1971 edition of Making Music Your Own edited by Beatrice Landeck, under the title "En Madrid (In Madrid)" but apparently in book 3 rather than 4, and on page 84. I'm very grateful for his help and for everyone who has already posted to this thread. I'll keep checking back here to see how things progress.
For my sister's purposes, even the addition of one more verse in English is helpful. She's a bit of a linguist, so I know she'll enjoy having the Spanish as well. My Spanish is not so good, but I think I get the gist of it. Thanks, Artful Codger, for posting this other version. It looks like the tune could be quite different, too, given the different structure of the verse.
I am supposing the English text from Making Music Your Own is still under copyright or I would post it here. The English I submitted for verse one is slightly different from what's printed. I guess that's the oral tradition at work.
Thanks again, everyone, for all your help.