One thing that caught my attention in the Songs of Holy Mary that we read was the role that religion played for the individual. Today, what I view as an increasing number of youth (in modern states) would consider themselves "nonreligious" but "spiritual", with religion having a connotation of being contrite, contrived, and overly regimented. The "spiritual" of today is in some ways the "religious" of yesterday.
In the Songs of Holy Mary, however, there doesn't seem to be any of this same desire for/orientation around a spirituality/religion that is "personally fulfilling", "intimate", or "self-improving" (today's spiritual). Quite the opposite, Spanish Catholocism was, in some capacity, a method of humans partitioning off tendencies and impulses onto other, external entities.
Cantiga 17 provides some exceptionally good examples of this. In implying that the devil coerced her into committing incest and was therefore guilty of her killing her baby, it is as though the devil is the cause of negative thoughts and doings. In many ways, the devil is what we would consider the role of justice, yet justice in Spain during this time was based on your religious affiliation. Due to the woman's Catholic faith, negative interactions and reactions are viewed as the work of the devil. Yet the fact that her deeds and thoughts can be passed off so easily as the work of the devil is almost like Jaynes' "bicameral mind". He theorizes that early humans, "when habit did not suffice to handle novel stimuli and stress rose at the moment of decision, neural activity in the "dominant" (left) hemisphere was modulated by auditory verbal hallucinations originating in the so-called "silent" (right) hemisphere (particularly the right temporal cortex), which were heard as the voice of a chieftain or god and immediately obeyed."1 While no one here is claiming to have heard voices, you have claimants having been made to do "evil deeds" by the devil. Inspiration in thought and into action is derived from outside one's self. (How real was this? Did people view this as the free pass that it was or did they take the outside inspiration to be, truly, outside?)
So in "loving god with all her heart", this is actually a relatively paltry statement of faith, if faith amounts to passing your actions and thoughts (both good but especially bad) off onto angels and demons. You would be the pawn of these "forces" and if they inspire your belief, then is it real? This woman can do what she pleases knowing that should things go south, it really wasn't "her" doing.
In that respect, it is especially attractive, both personally and politically. The individual, should they choose the right religion, is exempt, from nearly everything (as long as you ask for help). Delineating good and bad was also important politically due to the desire to Catholicize Spain. The more people that understood the distinction and understood the benefits of the "good", the more control could be gained for the court and their agenda furthered. It would seem that the Catholic religion, in serving a control-oriented political agenda, was a means of homogenizing the population (read more control) and these cantigas a means of proving that desirability of the religion.
1.http://en.wikipedia.org/wiki/Julian_Jaynes