Diddy Kong vs Rosalina & Luma

Stand close enough where you can react to SHfair. Be prepared to retreat to punish monkey flips. Once in that range, you don't need to press many buttons to pressure Diddy. It is often better to let him move first and react accordingly.

Land on a platform and work your way down from there, whenever possible. If Diddy Kong has a banana and there is no platform available, it is better to land near the edge. This way, if the banana does hit you, you will trip and fall offstage and not be susceptible to a followup.

Platforms are essential to landing vs Diddy Kong. Ban FD, and everything else is good for Rosalina.

A healthy Luma is only at risk of dying to Monkey flip (both the command grab and the kick). Luma will also protect you from banana either by blocking the projectile outright, or by being able to attack once you enter your trip state. Because Luma is so strong against Diddy's main neutral tool, it is very important to make sure you can anticipate or react to monkey flips. Once Luma has taken some damage, she is vulnerable to fair/bair kils from Diddy Kong, but even then, Rosalina will need to be close to the edge for Luma to die to these moves.