I mean, what's so bad with calling her Green (or if you like using the Japanese names, Blue)? Okay, I get it, if you don't pick a name for her she's called Leaf, but that's doesn't mean with have to call her that does it?
Other characters have default names too, like Silver default name can be Silver, Gold, Soul or Heart (depending on the version), so why don't we call him Soul then? Probably, because it's more awkward, right? Well I think Leaf is just as awkward.
And it wouldn't bug me so much except people insist you have to call her Leaf and I much rather call her Green (or even Blue). At least Green goes along with the other two's names. I mean, if your going to call her Leaf why don't you call Red, Fire and Blue, Water or something.