It's mar-gah-NEE-tuh and it's a scarlet pimpernel type plant that grows wild in
Israel.
The h is redundant really - it could also be
Marganita but that's how she spelled it (her father picked it out for her).
It's on at least one Hebrew name list online; I think the one linked to learnhebrew.com or similar website title (sorry, I'm not on my usual computer and in a hurry!)