>>717395915Y'know Daisy is probably the reason Peach doesn't reciprocate Mario's feelings. Like, at first she probably thought this random plumber who came to save her was super sweet and cute and kinda manly, and got a little crush on him...until Super Mario Land happens, and she realizes that Mario saving her wasn't a gesture of love, he just likes saving princesses. So when he goes and rescues Daisy, Peach takes that hard, and so she refuses to let herself feel love for him because she doesn't want to be let down and feel like she doesn't really matter to him.
Daisy getting with Mario's brother and getting plowed every night is just icing on the cake.