I love
Ivy! Tough, tenacious, irrepressible. Maybe that's less positive in areas where it's an invasive species. But it's a really lovely name, dark and evocative. It reminds me of playing amongst the trees as a child. Plus, it's so distinctive looking. It's youthful but not immature. (I also like Hedera, the genus name of ivy. It's a guilty pleasure though)
I think I've already that I don't like
Millicent. Millipedes aside, I've just realised it looks like it means "thousand hundred", which is altogether too many legs. But if
Millicent must go with something,
Ivy is a great choice.