In And Shine Heaven Now, Madeline, now a regenerator (immune to bullets, eternal youth, etc) and a member of the Holy League (the French branch of Iscariot), appears a few times:
The storyline 'Tu Seras Avec Moi', in which she crosses paths with Hellsing, to her ire, as they're both tracking the same vampire. She's stunned to find out about Seras, a vampire working with Hellsing, and later thanks them for their help in stopping the vampire (who turns out to be one of the other little girls Madeline grew up with).
Cameoed in "A Brief History, Of Sorts, Of Judaism", Erin's senior paper/comic, to explain when Judaism-the-religion and Judaism-the-ethnicity became two different distinctions (answer: when Napoleon emancipated the Jews in 1791).
One of the World War vignettes, in which she teams up with Lupin III to take down Rip van Winkle. He's stunned to find out she worked with his grandfather many years ago.
Erin had an idea for a story set a few decades before Shine began centered around Madeline, Pepito (who's now Madeline's husband) and a Muslim woman codenamed Mitraille. Unfortunately, it never got past planning the cast of characters.