That's right. What if that Habsburg oddball were to get hitched. Apparently relations with Matthias and Albrecht soured due to the fact that they "stole" Rudolf's fiancées for their own wives.
Now, from what I can gather, there were four main candidates (but if anyone knows of other possihilities please share):
Isabella Clara Eugenia of Spain (b. 1566) OTL Mrs. Archduchess Albert VII
Anna of Austria-Tyrol (b. 1585) OTL Holy Roman Empress
Maria de Medici (b. 1575) OTL Queen of France and Navarre
Margarita of Savoy (b. 1589) OTL Vicereine of Portugal and Duchess of Mantua
Personally, I thinking to have a certain Florentine banker's daughter as Empress would be fun, especially considering her bad rep OTL.