Changing it for her real name Makes no sense as
no one knows it is yet, not Baldr, not even Ignis knows, and at that current point in time she fully intend to take that secret to her grave ...
Just a personal opinion, but, I'm pretty sure her name is supposed to be Margot.
It is, the name Marguerite is also the key point of the next arc and the overarching Arc that'll go way to the future ...
Edit due to me misreading, Nope she call herself maggot, because she think of herself has one, it'll all get explained in the future