At the age of thirteen, Isabella was married by proxy King Christian II of Denmark.  Two years later, the Archbishop of Norway was sent to escort her to Copenhagen. 
The marriage was not a success, as the King had a mistress (known as 'The Dove') in residence, and would not hear of getting rid of her.  Besides, he was generally considered
to be mad.  After he had ninety-four nobles beheaded in the course of a single morning, the nobility turned against him (!)  He was deposed, and imprisoned in a tower, with a
dwarf for company.  
 
    After that, Isabella and her three children, Hans, Christina and Dorothea, were dependent on the charity of her brother Charles.  She died at the age of twenty-five.  
 
    Note:  Isabella's daughter was the Christina of Denmark made famous in Holbein's portrait, painted when Henry VIII was looking for wife #3.

Source: Sandra White