Responses
Well the FL is clearly settling for Casper and so is he. They get along well and might even live a good life together. But if they had a chance to truly be happy with the one they really love, they have the right to know and make that choice for themselves.
And the situation with Rachel and Ross is actually a bad example for what you said since Ross ended up saying Rachel's name during his vows...

This is like that clip I saw of Friends. Where Jennifer Aniston INSISTS she has to crash the wedding of the guy she likes because she HAS to tell the groom about her feelings for him.
Then Doctor House in the seat next to her says, that's selfish and no, she does not have to let the groom know her feelings for him, especially now that the groom's getting married.
So, like Arista here really shouldn't have spilled about ML's "true feelings" for FL. Reasoning that "she can't NOT know about his feelings for her", because FL doesn't really need the extra confusion and drama now that she's finally healing and moving on.