The obvious one is her down b that takes away Ness's recovery so easy. But most of her moves seem to out prioritize Ness. One of Ness's primary moves, PKthunder, is near completely useless with the luma blocking it and the Rosa down b. This also effects pk fire. Ness is a grab centric character to, which Luma can mess up.
Yeah, that makes sense. I was less scared of PK Fire during that match because of Luma protecting her.