For a girl?
I'd probably only use it as a mn. It is a family name and a couple of my male cousins have it as a mn (
Nathaniel Bellamy and
John Bellamy "
Jack")
I'm not usually one for surnames as fns and especially not on girls but I think it could be kind of spunky. Plus I kind of like Bell as a nn but don't like the frilliness of other -bel names. Bellamy isn't as princessy and overly girly but still feminine...I think.