@NndromedA you seem to have forgotten something mister. "she had reincarnated as the daughter of a Duke's house, by the time she regained her memories"
She was reincarnated not transmigrated. She lived her life as Iris for 18 years. She loved the prince that whole time. She didn't have memories of her past life since birth like other isekai reincarnations.
So yes, it was HER that suffered the love, jealousy, anger, and heartbreak. Not someone else and then she came into the body. It wasn't like that. So it's completely fair of her to say she's scared to love because something she nurtured for half her life didn't come to fruition.