Basically when (the current) Penelope blurted out "I love you" to Callisto in the maze, that wasn't really a lie because part of her (since she's also the original Penelope) meant it the same way words came out of her words when she told Reynold about original!Penelope's past in the attic scene... Some of the emotions she felt towards the Duke in the pre-coming-of-age ceremony scene was original!Penelope's as well.

She thought she made it up on the spot/out of nowhere but it all ended up being true: the fact that was had no money, couldn't read, was homeless and starving with her mother's dead body beside her until the Duke proposed to adopt her (cf. manhwa chapter 44). She knew because the current Penelope is a fragment of the original!Penelope's soul (the last fragment left).

Penelope's "I've been in love with you for a long time" felt true despite the fact that Callisto literally just came back from war because that was original!Penelope talking and the fact that Si Yeon/current Penelope felt compelled to play Callisto's path again and again (he's the ML whose path Si Yeon played the most) confirms it. She genuinely wanted to see him succeed and become an uncorrupted ruler because she loved him.

Ivonne also purposely got with Callisto and married him/was by his side at the parade to taunt Penelope and psychologically torture her, because she knew about Penelope's feelings for him (unfortunately, the hatred curse was still too strong at that point). She didn't need to marry him to get the Golden Tooth. Ivonne didn't do that because she had feelings for Callisto, it's obvious they hate each other and Winter, Eckles and Derrick were much easier targets to brainwash.