I need to write an article about a romantic story from Poland's history,
Gday Smurf - what about the love story concerning Pan Skshetuski and Helena in Ogniem i Mieczim?
Maybe try Pani Walewska and Napoleon
Good suggestion - Napoleon to Pani Walewska: "I see only you, I admire only you, I desire only you". If that doesn't smack of romance, then I'm a monkey's uncle!
Somewhat darker, though romantically underpinned, was King Zygmunt's devotion to his wife, Barbara Radziwill, who died young. If I recall, the grief stricken king took to wearing black after her death and never recovered.