Most people will never even know it's there. And if there's a family link, they'll understand. If there is anything to understand:
Marigold has been used, unlike, probably, Rhododendron -
Winston Churchill named a daughter
Marigold and nobody blinked. She died very young, and the couple's final daughter was
Mary, partly as a tribute to her late sister I would imagine. Plus, flower names like
Pansy and
Poppy get used;
Marigold has got to be better than them.
Juliet Marigold sounds pretty and distinguished, a name she can be proud of. Go for it!