I love Maribelle, but then again I love very frilly and girly names.
Marigold gives off more mature and less fanciful vibes.
Because Maribelle is so ultra-feminine, I would pair it with a simpler middle name. Some ideas off the top of my head:
Maribelle
IvyMaribelle
FayeMaribelle
NoraMaribelle
CoraMaribelle
EmmaMaribelle
RoseMaribelle
GraceMaribelle
Esme