Hola Tristan,

Others have researched the Monje de Leon/Alvarez Corona families. Silvia H. Corona comes to mind, and has published many studies available online. I’ve also posted some work I’ve done on this family here at NR: https://nuestrosraices.com/en/node/25061
That document from August 1594 isn’t Catalina de Leon’s testamento, it’s regarding her late husband’s estate. Throughout that document, Catalina Corona is identified as their daughter and heir. She was already married to Cosme Lopez and said that she was over the age of 24 years.
Catalina Corona is also mentioned in the testamento of her half-sister, Mariana Osorio, who was daughter of Catalina de Leon from her first marriage, to Cristobal de Giron Osorio, in which she identifies Catalina Corona, wife of Cosme Lopez, as her sister. She also bequeaths a slave named Maria to her niece, Doña Jusepa Corona, though she doesn’t say whose daughter Jusepa is. She also mentions another niece - a nun named Josepha de Jesus: https://www

Very interesting lead! Initially I too thought it seemed a bit far fetched however after connecting some dots I now think this has some traction! 

From what we do know, in 1641, around 10+ years after our ancestors Pedro Nieto and Josefa Corona married, they convened to the justices to affirm their marriage dowry. Josefa’s dowry was given to Pedro by Nicolas de Urdiales (Valdes) and his wife Catalina Lopez Corona! The sudden apparent need for it to be in written form was to “maintain the peace, amicability, and ensure no fraud to the dowry givers.” A second document confirms the receipt of the dowry, shedding light that it was originally agreed upon in 1630. The dowry was valued at 4,200 pesos and was loaded with goodies like; 

-a pair of blue silk sheets

-2 pink goatskin pillows with floral designs from Ruan

-5 Agnus Dei (cordero de Dios/lamb of God figurines) ornate with gold, feathers, and pearls

-10 spoons and 1 large ladle all minted of silver

-a decorative ornate salt shaker 

The

Wow. If I had seen the relationships given here on an online family tree, you know, one of those sourceless trees on which the relationships are based purely on matching names&surnames, I’d have ignored this. But this is the actual description of the contents of an actual file catalogued at an actual government archive; unless the documents are doctored, there is no reason to doubt the veracity of the relationships given. 
Many of us have wondered whether Josefa Corona descended from Martin Monje cc Isabel Alvarez Corona, and if so, how? This appears to confirm that, and reveals how. And you’re right, times & locations do match: a limpieza & probanza done for Josefa Corona cc Pedro Nieto in 1646, and the power of attorney to do so granted to her cousin, Lic. Martin de Leon (son of Pedro Villanueva and Beatriz Corona, who was sister of Catalina Corona), and before Francisco Morales (escribano publico and alguacil mayor in Sierra de Pinos). Btw, the name of the ancestor who was granted an