I can't help you with an URL, but in hard copy there's a book by Gabriela Mistral (from Chile) called 'Mødrenes sange. Udvalgte digte - Desolación' with Spanish and Danish parallell text. She writes about love and motherhood in that book, so there might be something in it for your grandmother. 'Mødrenes sange. Udvalgte digte' means 'The mothers' songs. Selected poems' in Danish.
A lot of 'free' poems in Danish are available at kalliope.org but since you don't know Danish it could be a problem. Perhaps you could try finding some poem there in Danish and then searching for a Spanish (or English) translation separately (guided by the name of the Danish author and some random Spanish words)?