Very sad indeed! It does appear that these are Anne's thoughts, and she is picturing Louisa and CW happy and in love. I had also been struck a bit earlier -- "Every report agreed in Captain Wentworth's appearing fixed in Lyme." -- as how Anne as much as anyone wanted to know what CW would be doing -- especially after we ended the previous chapter with Anne's pleasure of CW's deference for her judgment, even though it was "a sort of parting proof" which I take to understand that Anne looks at it as possibly her last interaction with him.