Story board made for Regendary, she does need lot of details and lot of help in her process. You may expect to see the story board pages way more detailled in a near future.
The story here is that Luna seems to keep her feelings for herself. Still traumatised by what happened with Celestia, she can't help but imagine that if she says the wrong words, she may be sent once more into the moon.
Also, Luna doesn't like Mi Amore Cadenza, that she sees as an imposter in many ways, especially her name.
Mi Amore Cadenza realises that something is wrong and try to make Luna open up, and it works...
To a point that Luna throws every frustration she got and almost turn Nightmare Moon during the process.
Realising that she went too far, Luna then tries to ask for forgiveness to Mi Amore Cadenza, assuring that she indeed feels a bit better but... Mi Amore Cadenza acts like a bitch.
Considering that Mi Amore Cadenza is a lost cause, Luna just decides to walk away.
Yeah, of course she'll go to the wedding. Sure.
But poor Mi Amore Cadenza did nothing to Luna during that dialogue. It was Chrysalis all along.