Super Mario 3D CAT

[Chaoxys]

Well, the Luma's seem to be smart enough to stay alive without Rosalina being by their side every minute (I mean, they survived before she showed up), plus, Rosalina is friends with Mario & co so it makes sense that she'd want to drop in to assist them. Also, she knows first hand that Bowser's plan can not only threaten the world, but the entire universe, which she seems keen on protecting. So yeah, he lending a hand makes sense and doesn't seem to cause any conflicts in terms of continuity or whatever.