Who is Silvia?

Who is Silvia? what is she
That all our swains commend her?
Holy, fair, and wise is she;
The heaven such grace did lend her
That she might admirèd be

Is she kind as she is fair?
For beauty lives with kindness
Love doth to her eyes repair
To help him of his blindness;
And, being helped, inhabits there

Then to Silvia let us sing
That Silvia is excelling;
She excels each mortal thing
Upon the dull earth dwelling;
To her let us garlands bring