It translates more or less literaly as:

The highly glorious Virgin, spiritual queen, is jealous of the ones she loves because she doesn't want them to behave badly.
I'll tell you about this a nice miracle that you will like (in which you'll find pleasure), the Virgin made it, Our Lord's mother, and by it, she freed from a great error a very false lover who, often, would change his loves, from one to an other.

I'm sure you'll put it in proper English better than I would.

I found a modern Spanish translation here