This is a fantastic question that, unfortunately doesn’t have an easy answer. My area of expertise is late medieval English history, and my answer will be mainly based upon my PhD thesis, which examined aristocratic marriage in the 13th-14th centuries.
The short answer to this is: medieval noblewomen were almost certainly involved in marriage negotiations, either for their own marriages or for those of others. We run into the same problem with this question as we often do studying medieval women more generally, however, which is that the sorts of documents that tend to survive (official legal documents as opposed to more personal documents like letters) also tend to be the sorts of documents that women were less involved in. As a result, there is a good deal of evidence for what men were up to and considerably less for women. Historians must read between the lines to infer women’s roles.
One particularly important note is that following the papal decretal Veniens ad nos in the early 12th century, legal Christian marriage could only be contracted by two parties of legal age (14 for boys, 12 for girls) giving their consent to the marriage. In theory, therefore, women could not be forced to marry against their will, because only freely given consent could create a legal marriage. We have no way of knowing how many women (or, indeed, men) were pressured to ‘consent’ to marriages they did not actually desire.
A woman’s role in negotiating marriage was affected by a number of factors: social status, marital status (i.e. whether she had been married previously), family culture, personal inclination and more. A wealthy adult woman of high status without close living relatives had considerably more power in negotiating marriage. The 1275/76 marriage between Edmund earl of Lancaster and Blanche of Artois, the dowager queen of Navarre, is an excellent example. After the death of her first husband, Henry III of Navarre, Blanche betrothed her young daughter Joan to the future Philip IV of France, then arranged her own marriage to Edmund of Lancaster, the younger brother of Edward II of England. The chronicler John de Trokelowe writes that Blanche,
'left alone without the comfort of a husband, honourably and wisely led herself and her court, so that many princes loved her and praised her. This lady's reputation for nobility and beauty thus travelled everywhere. And having heard rumour of the goodness, elegance and generosity of Lord Edmund, spread through many regions, her heart was ardently aroused in love.
Therefore since the rumour and reputation of each was similar, and they each heard so often of the other's fame, each one desired a marriage alliance with the other. After having received news and requested advice from their friends, the business was concluded. Their wedding was solemnised with joy and honour'.
Trokelowe’s account isn’t without fault – Blanche did not ‘wisely lead’ the court of Navarre, but rather was forced to flee it for the relative safety of French court. He also avoids discussion of the pressing and convoluted political motivations for the marriage in favour of a romantic account of each falling for the other’s personal characteristics. But, crucially, he plainly states that Blanche had as much involvement in the marriage’s creation as her future husband did.
There is other evidence of women following (or being allowed to follow) their own inclinations in marriage. One example is the trend of elite widows remarrying to men of considerably lower status after the deaths of their first husbands. In 1324, Alice de Lacy, the widow of Thomas earl of Lancaster, remarried to Ebulo Lestrange, a family servant. Jacquetta of Luxembourg first made a major diplomatic marriage to John of Lancaster, duke of Bedford. After his 1435 death she remarried to Richard Woodville, who had been a family servant. Perhaps most famously, after the death of her first husband Henry V in 1421, Catherine of Valois married Owen Tudor who was (you guessed it) a family servant. These marriages and others like them clearly reflect the women’s desires.
There are also scattered references to women’s involvement in marriages being organised their behalf. In 1398-99, Henry earl of Derby was negotiating for the hand of Lucia Visconti, the niece of Gian Galeazzo. There was concern that this was a poor marriage for Lucia, as the earl had fallen out of favour with Richard II of England and was in exile. Lucia told her uncle that ‘if she was certain to have the Earl of Derby for her husband, she would wait for him as long as she could, to the very end of her life, even if she knew that she would die three days after the marriage’. If Henry could not clear things up with Richard II, however, Lucia declared she was happy for her uncle to pursue marriage negotiations elsewhere. Clearly Lucia's opinion was being taken into consideration. In the end, Lucia did not marry Henry, but did make an English marriage in 1406, to Edmund Holland, earl of Kent.
A woman might also engineer a situation in order to marry a man other than the one her family had picked out for her. In 1340, Joan of Kent was married to William Montagu, heir to the earl of Salisbury. Years later, she claimed that before marrying Montagu, she had secretly married Thomas Holland. As a result, in 1349, the pope annulled Joan’s marriage to Montagu in favour of the marriage to Holland. The problem with Joan’s story, though, is that she was only 12 when she claims that she married Holland. Many historians (though not all, and this is a topic of ongoing discussion) suggest that Joan invented the story of the secret marriage with Holland to get out of a marriage she didn’t want and into a marriage that she did.
More common than these exceptional examples, though, are situations where we can at best infer women’s roles in marriage arrangement and negotiation. In the case of Henry earl of Derby’s (same as the above) 1380/81 marriage to Mary de Bohun, the two were connected by blood: Mary’s mother and aunt were first cousins to Henry’s mother. It has been argued that these women influenced the decision that Mary and Henry would marry. Research into these sorts of relationships – and the women’s roles that we might infer from them – is limited.
We also know from their surviving letters that Margaret Paston was deeply involved in decisions regarding her children’s marriages. The survival of the Paston Letters is a fortunate accident of history, which leads us back to the question of documentary survival rates. Medieval men and women did write letters to and from each other, but very few examples of these survive. If they did, we would likely have more evidence for women’s involvement in arranging and negotiating marriages.
FOOTNOTES
David d’Avray, Papacy, Monarchy and Marriage
Christopher N. L. Brooke, The Medieval Idea of marriage
James A. Brundage, Law, Sex, and Christian Society in Medieval Europe
Theresa Earenfight, Queenship in Medieval England
-----, ‘Highly Visible, Often Obscured: The Difficulty of seeing Queens and Noble Women’ in Medieval Feminist Forum
Theodore Evergates, ‘Aristocratic Women in the County of Champagne’ in Aristocratic Women in Medieval France
Chris Given-Wilson, Chronicles of the Revolution
-----, Henry IV
Calendar of State Papers and Manuscripts in the Archives and Collections of Milan, 1385-1618, ed. by Allen B Hinds
Linda E Mitchell, Portraits of Medieval Women: Family, Marriage and Social Relationships in England, 1225-1350
Kimberly Schutt, Women, Rank and Marriage in the British Aristocracy: 1485-2000: An Open Elite?
John de Trokelowe, Johannis de Trokelowe et Henrici de Blaneforde, monachorum S. Albani, necnon quorundam anonymorum Chronica et annales, regnantibus Henrico Tertio, Edwardo Primo, Edwardo Secundo, Ricardo Secundo, et Henrico Quarto
Elena Woodacre, The Queens Regnant of Navarre: Succession, Politics and Partnership, 1274-1512