Rosalina has some crazy Rage combos with Luma that can help get very early kills. Rosa-cancelled Luma aerials are very safe in neutral and can be a grab-confirm on shield. Luma in general makes it pretty hard to get in on Rosalina, so she's easily better than the other princesses. Peach is alright, has great ledge guarding abilities and some jank potential with rage, but ultimately gets walled out by Luma. Zelda is just garbage. Daisy isn't even playable.
“Rise like Lions after slumber
In unvanquishable number.
Shake your chains to earth like dew
Which in sleep had fallen on you—
Ye are many—they are few.” — Mary Shelly