Sure, there are lots of girl names that are flowers. Too many to list.
But Olive seems fairly unique as a vegetable (ok, fruit if you wanna get all botanical up in here).
There really aren't that many fruit-names, either. There aren't too many Apples, or Pears, or Oranges, or Kumquats. I mean... Cherry is probably more of a professional name for those who use it, if you know what I mean. Actually, now that I've fired up the Name Voyager, it looks like Cherry had a hey-day in the 1940s.
Maybe Olive is more named after the tree, but... there aren't that many tree names, either. Myrtle died out in the 1960s, and Willow has only just emerged.
Olive seems to stand nearly alone as a fruit-vegetable name.
Why do we name our girl-children after the sexual organs of plants, but not after their seedy little fetuses (except for Olive)?
Olive is even making a little bit of a comeback.
Also, I disregard any baby-name list that suggests a possible girls' name is Banana.