I love it. It is my little sister's name so I don't think it sounds too old. There are lots of great nns for it as well that you can use when she is young if you think
Marguerite is too much name for a little one. We call my sister
Daisy :-)
She is
Marguerite Siena Catherine by the way.
How about:
Marguerite RosalieMarguerite AlaiaMarguerite IsabelleMarguerite IrisMarguerite HeleneMarguerite AlessandraMarguerite Liora