Since she was independently wealthy and mature and could not have been compelled into a new marriage, this is about as close to a love match as it comes among the nobility in the late twelfth century—at least on her part. Balian’s motives may indeed have been more venal. The marriage was, however, explicitly sanctioned by King Baldwin IV.
First of all, younger sons marrying heiresses was actually extremely common in the Middle Ages. In the 11th and 12th centuries alone, the heiresses Adélaïde de Vermandois, Mathilde de Boulogne, Constance de Bretagne, Isabella de Clare, and Élisabeth de Courtenay all married landless younger sons. This was considered an ideal arrangement by the families of both parties, because it gave heiresses a husband to fulfill the military requirements of the title and it gave younger sons lands and titles without having to break up the family holdings.
Second, Maria Komnene likely had good reason to remarry rather than just solely because she fell in love. If she wished to protect the interests of her daughter in the kingdom of Jerusalem, she desperately needed a second husband to do so, especially because she had no blood ties to any of the nobility of Outremer. Furthermore, widowed wealthy women were a prime target for abduction by ambitious men who would try to claim their wealth and titles by marrying them by force. Marriage by abduction was not permitted under canon law, but it nevertheless happened and getting out of such marriages often took a lot of time.
