Did Catherine of Aragon use the title Princess of Wales before she was married to Prince Arthur?

Question

In several historical fiction books that I've read about Catherine of Aragon, she uses the title Princess of Wales as a child. I can't remember if the books were claiming that she used this title after her betrothal by proxy to Arthur in 1497, or after The Treaty of Medina del Campo in 1489, but I do know that it is mentioned in multiple books.

Did she actually use the title Princess of Wales before her marriage? Did she have a right to?

• Did the Treaty of Medina del Campo give her that right?
• Did her betrothal give her that right?

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ETA: I found an example

"We will be burned alive!" Madilla, her servant, screamed behind her. "Run! Run and hide!"

"You can be quiet." The child rounded on her with sudden angry spite. "If I, the Princess of Wales herself, can be left in a burning campsite, then you, who are nothing but a Morisco anyway, can certainly endure it."

The chapter takes place in 1491 (The Constant Princess, Philippa Gregory)

Answer 1

It would have been treason for any English subject to do so.

Absent the Battle of Bosworth, Catherine had a stronger de jure claim to the English throne, through descent from John of Gaunt's first and second wives, than Henry VII had descending from John of Gaunt's ex post facto third wife, Katherine Swynford. To address her as Princess of Wales, prior to her marriage to Arthur, would have been granting her right to that title in her own right - and thus accusing Henry of usurpation. With the Tudor crown not quite yet sitting comfortably on Henry VII's head - no such action could have been allowed to stand unpunished.

As for Spanish emissaries or ambassadors, such action would have been unlikely for different reasons. Spain was eager to make an alliance with wealthy England in the immediate aftermath of the just completed Reconquista. Although immune from any direct punishment for treason - Henry not being their monarch - he would have been well within his rights to expel any Spanish diplomats who he saw as fomenting treason. Likewise the Catholic Monarchs would have undoubtedly been displeased to suffer such an embarrassment with a potential ally.

This is not to say that simple statements of fact, or presumed future fact, would be disallowed. Statements such as

You will be Princess of Wales after your marriage. You must act appropriately.

would have been most acceptable. Likewise Catherine was a Spanish infanta in her own right, Spanish equivalent of any legitimate English child of a reigning monarch, and entitled to be addressed in a manner befitting that rank, whether in Spanish or English.