Abrielle was completely puzzled by the way Alfonso was acting. He was acting out of character. She had never imagined Prince Alfonso to have a liking of any kind for the wife of his brother who was known for her obsession.
Although he wasn't a saint because he was known as an infamous playboy, in the actual novel that was yet to start. Alfonso had a couple of illicit affairs with titled nobles' wives to gather support.
It was his strength that was later exposed in the book when he was killed by a nobleman who caught him and his wife hitting it off secretly in a garden during an event. The man could not bear the betrayal and killed Alfonso and his wife.
That was a tragic end for him. Alfonso had only one reason to be approaching Abrielle and that was to use her because of her family support. The Nightshade duchy was one of the king's right-hand men which was while Abrielle's and Cedric's wedding was delayed.
