Ehhh that's very argueable to be honest.
It's not secret that most fans and not fans of the character have a noticeable preference for Mercedes Rose portrayal as Rosalina ; because above all details and reasons , bottom line is that her ''Rosalina'' standed out the most between , her , Kerri and Laura.
When i had a little conversation about it with Kerri Kane , the best guess she could give me was that the first recast was most likely because they wanted someone that sounded significantly younger for Rosalina , which can be considered as true since both Kerri Kane and Laura Faye Smith , while not sounding similar , at least sound younger and significantly more cheerful than Mercedes Rose did.
Little did Nintendo know , that nobody really appreacited this sudden change as it was really not needed to be quite honest.
This role in the end would be in the hands of Kerri Kane if she didn't relocate from seattle to california , and that's why she dropped Rosalina and the reason of Why Laura took over.
Now , what i don't get , is why they didn't recast a match for Rosalina that sounded like Kerri Kane?
While Kerri sounds significantly different than Mercedes , they both have the ''it'' factor that makes you say ''oh that's Rosalina and not Peach'' for example. And it's not really the filter , it's just how they speak and deliver.
While i have been very critical of Laura's portrayal in recent installments , i must still question why Nintendo decided to cast her when she doesn't sound like Kerri Kane whatsoever. It makes sense she doesn't sound like Mercedes because the point of all the recasts was to find somebody else that was not sounding like her , so that's it , but still i don't understand it.
No shade to her though , since i particulary enjoyed her First take on Rosalina in SM3DWorld which was really good , especially comparing to Mario Kart 8 which wasn't the worst in the game , but it's totally a weak portrayal comparing it either to 3D World or to MK7 or MKWii .
I have come to the conclusion that Laura can portray Rosalina just fine , but then again , this is not what Nintendo wants. It has been perfectly clear by the fact that Rosalina has 100+ sounds in 3D World which are just fine , and yet most appearences of Rosalina featuring Laura's vocals use MK8 clips , which are the ''bad'' ones since they are just soooooo happy to fit her facial expressions.
In other words , blame Nintendo as usual , for fixing what was not broken.