It was at a friendly meeting at Rieti where Pope Gregory suggested to Emperor Friedrich II that he marry Princess Isabella, a sister of King Henry III of England. At first Friedrich II was concerned to lose his French allies; but when he realised that an English marriage would end English support for his opponents, he agreed. 
The beautiful Isabella was about twenty-one years old when she set out to marry the twice-widowed Emperor Friedrich II, who was forty. On her way through Cologne, she delighted the local women when she removed the traditionally worn veil so that they could see her face. 
She also brought a considerable dowry with her. 
However, as soon as she was married she was introduced to the secluded harem life attended by black eunuchs. The marriage was consummated the day after the marriage ceremony. Although their marriage had been a political match, it still seemed cruel when she was allowed to keep only two of her English women-attendants; the others were sent home. Like all women in the thirteenth century, it was clear to Isabella that her only function in life was to produce children to secure the succession. In all she gave birth to four children but only two survived her. 
Isabella lived in retirement at Noventa where her husband regularly visited her. When her brother, Richard, Earl of Cornwall, returned from the crusades, he was allowed to visit her although 
Isabella was not allowed to be present at the official reception. while the imperial court resided at Foggia, Isabella gave birth to her last child and died. She was only twenty-seven years old and was 
buried in the Cathedral of Andria. 

Source: Leo van de Pas