Sorry for coming into this discussion so LATE!
Here's my two cents' worth:
She reflected on (this verb can also mean that she "described" aloud, for the benefit of other people) her devotion, of which she had given ample proof
(lit: "shining proofs" ), well before her relationship with the prince had been sanctified by marriage.
Just to clarify, she is now married to the prince, and is reflecting on (or describing) her devotion (to him, one could assume), and her previous actions which expressed that devotion.